but it rests on the again implicit assumption that a simple change of environment allows everyone to thrive equally
This is emphatically not true. The SCS Noonan Scholar program is a very successful program for underrepresented minorities. Initially, they tried just giving money and a seat at an elite institution (Harvard, Amherst, that caliber), and they found that their students failed out of STEM subjects with regularity. So now they offer summer programs where they teach the subject and soft skills, i.e. time management, networking, & so on. This improved outcomes enormously. At Cornell they do the same. For some admits their summer program is mandatory.