Essays for admission are never (at least when I went through the system) done under observation - they're take home assignments which makes them really easy to game.

Interviews by alumni honestly seems like a pretty good evaluation metric - it is quite susceptible to legacy favorship though.

Think the problem is more with extracurricular activities. If you are well off, it easier to let your kid go to piano lessons, do some volunteer work, join a social mission to Africa during summers, etc.