Your point isn’t coming out like you think. What you just said was 80% of the student body is middle class.
No, what was said is that ~15% of the student body is in the top 1%. The top 5% by income make up 42% of the student body. I'm not sure about your own definition but I wouldn't qualify that as middle class.
I don't view 95% of the population making up 58% of the student body as an indicator that we're doing things particularly well. Especially when you don't ignore the fact the bottom 20% make up only 3.8% of students and the bottom 60% of the population only account for 18%.
These statistics fly in the face of any belief in meritocracy, social mobility, access to education, academic achievement etc. They imply either the children of the top 5% are genetic superhumans or that, as a society, we're failing spectacularly at living up to those goals.
The children of the top 1% make up 14.5% of the admissions to these schools. The chart of students by parental income[0] speaks for itself.
The children of the bottom 20% make up a mere 3.8% of the student body. I'm not sure how anyone can look at the current situation and suggest there's nothing wrong with it.
Perhaps these people are inherently inferior? Instead, I would suggest that we should do something about the talent that we're intentionally wasting.
[0] Chetty R. et al, Figure I. B, MOBILITY REPORT CARDS: THE ROLE OF COLLEGES IN INTERGENERATIONAL MOBILITY, Page 80. url: https://www.nber.org/system/files/working_papers/w23618/w236..., image: https://i.redd.it/tbh2qmozodv91.png