While I agree with you that vague assessments like "well roundedness" can and have been use for racial discrimination in the past (both intentionally and unintentionally), it doesn't mean we should throw the baby out with the bathwater and solely use standardized tests or test scores to determine admissions.
There is critical value in assessing these hard to measure qualities for creating a student body. Each student in the university is not simply consuming an educational good in isolation from one another but is also offering their experience and perspective to the community. Having everyone maxed out on test scores at the expense of such diversity would be a travesty to the thing that makes campus life vibrant.