Why does Captain America not land in the same place after time travel?

After the time travel why doesn't Steve Rogers land in the same place(the time portal), rather he seems to be sitting on a bench near the lake!

Because he didn't time travel to get there.

Steve travelled back to an undetermined point in the past to be with Peggy Carter and stays there.

He then lives out his life in normal time and then goes to the lake when it's time for him to show up.

Now, granted we don't see him walk to the lake, but that's for dramatic effect. It has nothing to do with travelling through time to reach the present.

We can only speculate. Perhaps he used tech from his timeline to return silently in a slightly different location.

But what we do know is that when he traveled back to see Peggy Carter, he created an alternate timeline, so he cannot have just lived out his days with her and then traveled to this scene without somehow jumping timelines. He must have traveled back to his origin timeline somehow. We know for sure that, in the MCU, time traveling creates new timelines that don't affect the timeline they left, and this is unambiguously established by the rest of the movie.

Script thanks to this wiki:

RHODEY: Wai-Wait a second, let me ask you something. If we can do this, you know, go back in time, why don't we just find baby Thanos, you know, and... [he makes a hand gesture suggesting that they strangle baby Thanos with a rope.]

BRUCE BANNER: [Disgusted] First of all, that's horrible...

RHODEY: [In a tone that says it's what we're all thinking.] It's Thanos.

BRUCE BANNER: ...And secondly, time doesn't work that way. Changing the past doesn't change the future.

(Emphasis mine)

The movie makes it very clear that changing your past doesn't change your present. The whole movie is totally consistent with this apart from the scene in question:

Present day Cap didn't fight an older version of himself back in 2012.

Present day Loki didn't escape with the space stone in 2012.

Present day Nebula didn't help her boss travel from 2014 to the future and die.

We know this because we saw how these happened to our main characters in other movies.

We have no reason to believe anyone in our timeline has ever co-existed with their future selves, and no reason to believe an exception was made for Captain America -- unless old Steve is from a different timeline and travelled back to this one.