Can you name the schools, majors, and the specific complaints from those at each school and major?
For example, the University of Arizona is an AAU school, but automatically admits Arizona residents with top 25% class rank, and admits more than that, so it is not surprising that some students need remedial course work. And it has impacted majors like chemical engineering which requires a 2.30 college GPA to change into, which is not that high a bar. Somehow, I do not see the University of Arizona (and Arizona’s two other public universities) choosing to admit only the top end applicants who are almost guaranteed to succeed, while leaving most of its capacity unused and wasted, and leaving most Arizona students who do have some chance of success in college unable to try to realize their potential.
You are assuming that elite schools admit a non-trivial number of students who are unlikely to succeed. Where is the evidence for this, given their extremely high graduation rates?
You are also assuming that faculty have no input in the admissions process. It is rather likely that, at most or all of these schools, faculty have substantial input in shaping the admissions process and criteria, even if they are not involved in the operation of the admissions process (reading the applications, etc.).