If you treat prestige acceptance rates as a derivative of the progression of racial policy, it absolutely makes sense why affirmative action is in place given the history of racial justice in America.
Can you really claim that the trend won't reverse if purely meritocratic admissions are reinstated (disregarding legacy admits...although very unfair to disregard since their racial makeup heavily tracks with asian/white/etc)
It's simply a single lever to change the racial makeup of the upper class. And certainly it goes both ways, but to simply remove it with no solution implies a regression to the former system, which was all but equal, much less equitable.
Why are we treating it as a derivative, and what's the slope? Do we have proof it's not zero? Let's say Johnny and Kareem both study poli-sci at Harvard. When Johnny graduates with his gentlemanly C's, his dad puts in a word with his golf buddy and it's off to Wall Street. Kareem shoots his resume off through online portals but no one bites. He goes to law school and takes on even more debt. Johnny's sister, Sally, passes the bar on her third try and is hired by a white-shoe law firm. Et cetera.