Either we leave hooks, or they all are eliminated and it becomes more if a numbers game. They are building a class, and like race, culture, region and socio economics, continuity of relationship with the school is a part of what some schools want.
I’m sure there are as many unqualified URM or first gen admitted as legacy kids that slip in. It happens now and then that they don’t end up performing or living up to the task. (Again, legacy, not big donor. I can’t imagine the big donor admits amount to many.). Overall, those groups all do well.
As for the legacy and donations: a school is always courting the big donors, but their bread and butter are the rank and file alum who give a few hundred a year. If their kids go, so will they. And maybe mom and dad will bump up to a few thousand a year. This is how they get those huge endowments. And those huge endowments are how they pay the first gen FA.
Be careful what you wish for…