MIT does no legacy admits, because the core curriculum required of all students is so much harder, e.g. lots of calculus and physics, vs. Harvard in the '80s requiring you to prove you can do algebra. So MIT doesn't admit anyone they don't think can "do the work". although if you make that cut I'm sure it doesn't hurt to be the child of an alum, but it didn't come up all that often in the '80s at least.
MIT specifically looks for evidence that applicants can do projects. Beyond that, as far as I can remember they're pretty generic in trying to construct a class (trying since yield, acceptances of admission offers, is very hard to predict), favoring the things every high end college looks for such as geographic diversity (both of those helped me a lot).
So the very first thing strongly aligns with the school's goal of overall being an "egalitarian meritocracy"; what you do and can do is where it's at. MIT students do not as a rule aspire to be lower tier corporate yes-men.
Caste system survived because an exclusivity principle was employed to keep the lower caste's out of systems which could benefit them on the longer run like education, employment, religious institutions.