Is Mindy St Claire the best person in 500 years?

Maybe

During the episode Jeremy Bearimy, Michael mentions that his experiment of the "Good Place" took over 300 years to complete. However, he explains that since the timeline in the afterlife looks like a cursive "Jeremy Bearimy" that loops back to itself, he is able to send the humans back to their bodies at the exact time they died.

So given that, we know that the time in the afterlife does not run parallel with time on Earth. It's really difficult to tell what 500 "years" in the afterlife looks like to humans on earth. Maybe it's the year 2500 on Earth by the time he says that. Maybe one loop of "Jeremy Bearimy" is only a day on Earth. It's hard to say.

The reason why no one has been getting into the Good Place is because of the impossible tangle of dependencies and interactions that go into any action you make on Earth—that is, no matter how good something you do is, the ripple effects cause so many negative points that they outweigh the good points you have earned.

Note also that “the negative points outweigh the good points” is not the same as “the harm you do outweighs the good.” That isn’t part of the thesis of The Good Place at all—the points for everything are fixed the first time the action in question has ever been done, which means that their relative point values later may be—really, must be, considering the outcomes we see in the show—wildly out of sync with the actual good or harm done.

The point is that the system is arbitrary and rigid. It’s literally “damned if you do, damned if you don’t.” No matter how much good you achieve, actually doing the good work itself costs you more points than it earned you, even if you game the system like Doug Forcett.

But Mindy St. Claire never actually carried out her plans. Mindy St. Claire had the best point total in centuries, but that doesn’t mean she’s the best person—it means she side-stepped the flaw in the system that’s damning everyone else. It would appear that the system gave her credit for the good plans she drew up and the good she indirectly caused, but didn’t penalize her for the ripple effects of actually implementing them.

So no, Mindy St. Claire isn’t the best person in 500 years, but she is the person with the highest point total in 500 years. Just another demonstration of how horribly flawed the system is.

The answer to that is a definite "maybe".

The question of Mindy's moral worth is not answerable within the systems used by the Good Place and the Bad Place, which is why Mindy ended up in the Medium Place.

Bear in mind the exact circumstances that led to her unique situation: She lived a slightly below-average human life, being a selfish, cocaine-addicted, sex-addicted Wall Street type until she came up with a plan to start a foundation that would channel her wealth into good causes. She wrote up the plan in great detail, and then died shortly afterwards before putting any of it into action. It was her sister who actually carried the plan out. The representatives of the Good Place were thus faced with a dilemma: given that she didn't actually create the foundation itself, but she did draw up the plan and it wouldn't have existed without her, does Mindy get the points for the foundation's good works?

If her previous life produced a points total of, say, -50000, and the total required to get into the Good Place is, say, 100000, the total point value generated by the foundation would be around 150000, which would be enough to get her into the Good Place... if it counted. But did it count? The Bad Place people said it shouldn't count; the Good Place people thought it should. They couldn't come to an agreement, hence the compromise of the Medium Place.

If the foundation-related points are allowed to count, then yes, Mindy is the human with the highest point total in 500 years. But does this mean that Mindy is the "best" person in 500 years? I don't think so, although this is admittedly speculative. Mindy's post-death personality is not good: she's selfish, hedonistic, and doesn't seem to care about others at all. It's likely that if she had survived, even if she had carried out the foundation plan, she would have accumulated more negative points just by living the same kind of terrible life she'd been living all along, and her point total would ultimately have slid into the negatives.

If anything, I think Mindy's case is designed to show up the flaws in the Good Place/Bad Place system. Considering her character in the round, there's no meaningful sense in which Mindy is a better person than Chidi, and yet Mindy is spared the Bad Place, essentially on a technicality.