Although I wouldn't contest your opinion about "ceilings" etc, because I don't know much about it, I would contest that elite universities select from a pool that is above most people's top end. I suspect the average intelligence of Harvard, MIT, or Stanford students is higher than the national average but still within the first deviation - in other words, most people in the population who are interested in university are probably "smart enough" by nature to succeed at one of these schools.

Socioeconomic factors playing a role (even a majority role, in my opinion) in access to elite education isn't about $20 million gifts. It's about living in neighbourhoods that have good primary and secondary schools; it's about living around peers who think going to university and even elite universities is normal and achievable; it's about being able to afford "personal rounding" activities like organized sports or music lessons; it's about being rich enough to be able to afford to give volunteer hours.

This "privilege" doesn't make those people bad or invalidate how hard they worked, but we should avoid thinking their success is due to some innate, "natural" superiority like just being smarter.