Thanos's choice made sense for Thanos as it has worked so far. When his planet was going through a crisis no one acted on the plan he postulated. Perhaps because of the mass genocide he was offering them. Lets assume that the people who shut his ideas down came up with some noble idea of saving the planet without killing half the population. It miserably failed. But his idea of killing masses has saved Gamora's planet and a no. of others. So for him its the only way as he wants to do what he could not for his own planet.

Thanos already had proof that wiping out half of a civilization works and this was with Gamora's homeworld.

In a flashback we see Thanos take a young Gamora as the Chitauri are separating the people into 2 groups before wiping out one group. Later when Gamora questions his actions in the present day, Thanos explains that since he wiped out half of her people the civilizations has been better off now that there is enough resources to go around.

He also explains to Tony, Peter and the Guardians about the planet Titan (his home) showing them with the Reality Stone what it used to be, how he proposed random selection for culling half of the people but when he was ignored Titan ended up in ruins because of the strain on resources

There is also the possibility that by killing people he is trying to get Death's attention. In some of the comics (and I admit I don't read them, this is second hand info) Thanos has a fascination/crush/obsession for Death who in the Marvel Universe is manifested as a woman.

At the end of the first Avengers film in the post-credits scene The Other says to Thanos (who we haven't seen at this point)

Humans. They are not the cowering wretches we were promised. They stand. They are unruly, and therefore cannot be ruled. To challenge them is to court death.

Then we see Thanos's face and he smiles. This could be an indication that in the MCU Death is a person and that Thanos is hearing "court" as a verb which in that context it means

1. Be involved with (someone) romantically, with the intention of marrying.

2. Pay special attention to (someone) in an attempt to win their support or favour.

Thanos repeatedly notes throughout Infinity War that only he has the willpower to do what needs to be done and he will not be dissuaded or deterred. His unrelenting will is his defining character attribute -- and apparently a prerequisite for mastering the Infinity Stones.

When his planet, Titan, was in distress, Thanos determined that the only solution to overpopulation was to kill half the population so the other half would have more resources. If that's the solution to the problem(s) that Thanos sees, that's the solution his unrelenting will seek try to enact, even on a universal scale.

He can't choose to solve the universe's problems another way, by increasing the amount of resources available, because that would mean he was wrong to try to kill half of his people. (It's also possible he's an unreliable narrator, and he wound up killing everyone else on Titan because they resisted his proposal to kill half the population.)

We also see at the end of the movie that his drive doesn't extend beyond enacting his solution. As he envisioned, after carrying out his plan he has retired to a hill to watch the sunset. He has solved his problem; he doesn't appear to want to rule the universe (nor does he appear immediately capable, given the state of the Infinity Gauntlet).

Thanos is not human. He'll make any sacrifice he has to make. He can't be reasoned with; he won't see the arguments of others; he won't consider alternatives. He is irrational; he is The Mad Titan.

Thanos is a mass murderer

(Please note that the following is my interpretation)

Thanos is, to me, an analogy to historical figures who also went on to commit genocide. He is charismatic leader who feels wholly justified in his actions.

When looking at historical mass murders, regardless of motive (political, religious, economic, racial...), those perpetrating them always felt like their actions was the best possible course for the greater good.

Be it the ethnic cleansing in Rwanda, the raping of Nanking, the systematic murder of political dissidents in Franco's Spain, the obliteration of natives by European colonists, or, of course, the genocide carried out by the Nazis.

All those, and more, were, to the people perpetrating them, totally justified, and the "only way" to solve a terrible problem.

Yet, had we personally met any of the leaders behind those acts, we'd have found they were very similar to Thanos, not hideous monsters bent on doing evil, but actually very likable people with the ability to compel others to their point of view.

This article is a good read on the subject: Cracked.com: 5 Reasons Horrible Dictators Always Catch Us Off Guard

In my opinion, the main thesis of the movie, reinforced by the "we don't trade in lives" catchphrase, is that, no matter how noble your motivations, the moment you decide on a course of action that instrumentalizes or outright seeks the suffering or death of others, you fail the most basic test of humanity, and turn into a monster.

I also think this is further reinforced by Thanos' "sacrifice" to get the Soul Stone. He claims he feels love, yet he intentionally hurts the one he loves, which, in real life, is a red flag for abusive behaviour.

So, again in my opinion, the point of the movie regarding Thanos is that, despite his lofty goals, his charisma, his self sacrifice, or his tortured feelings, he is nothing more than a callous mass murderer.

Which should be obvious considering he is the movie's bad guy.

Thanos' plan doesn't make any sense on many different level.

1. Life doesn't "destroy" resources. Atoms are used but then returned to the environment. Plants get their energy from the sun which would be burning regardless of whether or not it is harnessed. Technology, infrastructure, and social constructs are the most important things when dealing with industrial agriculture and its ability to produce resources for people. Coming in with an army and randomly killing 50% of the population will utterly devastate that. Thanos should be conquering planets for his empire and then expanding investment in advanced agriculture technologies and instituting birth control mandates once the planet reaches the new max pop (new max because of the advanced tech he can provide increasing their max far beyond current pop). His plan is actually counter productive.
2. Fighting back against him because he is genocidal costs a lot of resources, a lot more than mere agriculture.
3. Lets assume for a second that he is right about resource limitations. Why does he arbitrarily insist on 50%? planet X could need 70% culling and planet Y could need 10%. Thanos doesn't care, he always goes for 50%.
4. A one time culling of 50% will be quickly recovered from
5. As china's "one child policy" shows, you can use birth control instead of random killing.
6. Planet's contain trivial amounts of resources compared to space, and they are a bunch of space faring races. Even if planets are overpopulated, it doesn't mean the galaxy is.
7. The infinity gauntlet can literally create free energy/matter/etc instead of murder.
8. The infinity gauntlet could be used to just make all races less fertile

Well, for starters Thanos is referred to as the mad Titan. He had one intention, to make a better universe, but he didn't had a plan per se.

He wasn't that kind of a person who would lay out plans, increase resources in some way and save all the population. He had powers and loyal (or at least fearing) army who would blindly follow his orders.

In past he did genocide on a couple of planets (like gamora's) and whatever the reason may come, he found the planets to be more happy and peaceful now. So he continues to follow that path.

And Thanos is that type of character in a story who desries to rule entire universe, and in the midst of that, a wrongly intended aim of making the universe a better place.

Thanos' choices make a kind of sense in his (highly warped) worldview

One source that helps us to narrate this is Ebony Maw, who acts as a kind of herald and high priest for Thanos when a culling is underway.

EBONY MAW: "Hear me and rejoice! You have had the privilege of being saved by the Great Titan. You may think this is suffering. No... it is salvation. The universal scales tip toward balance because of your sacrifice. Smile... for even in death, you have become children of Thanos."

and again:

EBONY MAW: "Hear me, and rejoice. You are about to die at the hand of the children of Thanos. Be thankful, that your meaningless lives are now contributed to the balance…"

When Thanos meets the infant Gamora for the first time, he gives her a simple lesson with the aid of small, perfectly balanced bladed weapon.

THANOS: "Look. Pretty isn't it? Perfectly balanced, as all things should be. Too much to one side, or the other... Here. You try. Uh-uh. Concentrate. There. You've got it."

Here we are getting to the heart of Thanos' insane ideology. The welfare of the universe, and of all living beings, rests on maintaining a 'balance'. Too much either way, and total destruction is assured.

Thanos believes that culling half of life in the universe will restore the universe to balance, which is ultimately the most compassionate thing to do!

One question is whether other methods of restoring balance, such as reducing birth rates, would do just as well. But all that really matters to Thanos is this 'balance' and so that needs to be corrected as quickly and bluntly as possible. As Ebony Maw says, individual lives are worthless in comparison to the maintenance of this cosmic 'balance'.

However, there is no evidence in the MCU that any such abstract 'balance' of lives exists, and so Thanos' messianic mission to restore this balance is an appalling madness and idolatry. Thanos actions make sense according to his worldview, but his worldview is an insanity.

Resources can't be created out of no where, a certain balance of thing always follows, as in Marvel comics(and hoping the same for MCU), there is always a balance in good and the bad(matter or power or good/evil). For example Galactus was once turned into a life saver than a destroyer, so to maintain the balance between good and bad, he had to undo the process, making him a planet eater parasite again !!

Coming back to your question, this was solely Thanos' view, and he wanted to stand on it, if someone would come up with a different or conflicting solution, he had to face the wrath of the mad titan !

Thanos can make more, but he really shouldn't.

No "right" or "wrong"

First off, when looking at the problem of overpopulation, and this specific solution, there is no right or wrong answer. There isn't a catch-all solution that will work in anyone's favour. There is only what one chooses to do.
Similarly in the real world many problems have a multitude of possible solutions, each solution having its pros and cons and in the end only one of these possibilities is chosen and acted upon, carrying with itself all consequences of the choice.

Thanos could have just "made more" but he chose not to, many people in his position would have done the opposite, many others would do the same.

Why "more" is bad

The Infinity Stones are objects of great power, even more so, considering they are imagined in a comic/movie. But still, in order for anything, be it a comic book or a movie, to be at all relatable there must be at least some basic real world principles followed. The moment your object/character/superpower ceases to follow any rules, limitations or at least the very basic physical principles - you loose any relation to the audience and the whole point becomes moot. It would be like arguing why Salvador Dali's Clocks are melting, when they should be standing firm.

Having said that the one law of physics that always MUST be observed and that nothing can escape from, be it a star, a planet, an atom or even light, itself, is the Law of Concervation of Energy.

What that law says is that the amount of energy (and thus, matter) in the Universe is always constant. You cannot create or destroy energy or matter. You can only transform it from one form into another.

"More" means "less"

What this means is that if Thanos were to create more food for all people (assume I mean all sentient creatures when saying "people") he would have to take it from somewhere, in effect only hastening the diminishing of resources.

Overpopulating faster

If you have more food you are going to populate more and faster, only bringing the problem faster and worse than before.

Running out of space

You could argue he could just make even more food every time. That would be worse and worse each time, for starters - you would soon start to run out of space, as in ground to live on (since you would increase your population even faster each time).

Economic strain

More food that just appears out of nowhere would crash every economy that has producers and marketers of food. Prices would have to drop to compete with free food "falling from the skies", which would lead to cutbacks, layoffs and in many cases the government would have to step in and limit access to this miraculous sustenance.

Additional needs

The problem becomes even worse when you take into account people need more than just food. The new populations born thanks to more available food are going to need clothes, jewelry, luxuries, etc. Giving them that with the Infinity Stones would diminish the Universe's resources even faster, crash the economies even worse and so on.

Excess is bad

Humans (and therefore all movie aliens) are built on the premise that there isn't enough and often there might be nothing at all. Our entire function, like any animal, is geared towards surviving the harsh world as best we can.

• When well fed animals will abstain from unnecessary actions to conserve energy.
• When animals find food they try to eat as much as they can to the point of vomiting.
• When any one of our basic needs isn't satisfied we are focused towards satisfying it. Conversely when a need is satisfied its safeguarding is usually forgotten or disregarded.
• The whole point of "ambition" is the desire to be in a better position in life, you can only strive towards a better position if your current one lacks something

Keeping all of the above in mind if Thanos were to satisfy all needs of all people there would be terrible social degradation. No one would work, nothing would get done, skills, knowledge and great works will be forgotten, society will devolve to obese, lazy creatures. Like a behavioral sink.

No good deed goes unpunished

Presumably the Avengers wouldn't want to stop Thanos if he wanted to create more in the Universe but every single major corporation in the entire Universe would. And that would be much worse than the Avengers.
Even disregarding that something very important has to be taken into account - Thanos isn't obliged to supply people with more, like said before if he were to do it once, he'd need to do it again and again and again... As we saw that takes a lot of effort and energy. Effort no one is going to thank him for, effort that will only be met with complaints and critique. In short - doing that would quickly make him regret it.
If you think that is far fetched, even our current daily lives are full of examples where people try to do good but are rarely thanked and abundantly critiqued for that.

Sheep in a pen

Consider this:
If you were a farmer with a bunch of sheep in a pen and a pasture and those sheep multiply, as animals do, to the point where the space in the pen runs out do you build a bigger pen and find a bigger pasture? Do you do this every time to the point where you need to spend 12 hours a day maintaining the pen and the other 12 herding your sheep across half the county to get them to enough pastures to feed them?
Or do you sell/kill half?

Now, the obvious argument some people would make is "But sheep aren't sentient.".
You only think sheep aren't sentient because humans are much more powerful than them and know a lot more than they do.
So in Thanos' eyes humans aren't sheep. Because sheep at least are useful.