It's a shame that we're here in 2021 and the best we can do is basically just "selection bias." Basically all universities have no statistical proof that they can educate people beyond this. This is not to say that the schools are bad, but most of the education is simply due to the types of peers you have, not really due to the school itself. Princeton and Harvard admit, for the most part, people who already excelled…
If you talk to the admissions department of every top school, they will all admit that they reject a large number of perfectly capable students.
So why don't they try to expand their programs and increase their acceptance numbers? I can only guess. Scared of change. Politics as well, I imagine. Afraid of not appearing selective, pissing off alumni, that sort of thing. [1]
It's depressing to me how hard it is to get into a top school these days. I bet many of us who went to an amazing school 10-20 years ago would be unable to afford or get into that school today. If you wanted to get into MIT 40-50 years ago, and you were capable, you were pretty much guaranteed a space.
Something has to change, or extreme class divides will just keep on growing, and meritocracy will become a distant memory.
[1]: A notable exception being Georgia Tech's OMSCS program. They basically admit anyone who wants to get in, and offer the program at cost, so 7k for the entire thing. Graduating is another matter entirely - it's very difficult. The goal of the program is specifically to offer a high quality education to anyone who wants it. It's been an interesting experiment, and shows what is possible.