See, the parents of white (and Asian) kids have, or can buy, access to social networks that underrepresented groups (particularly black and indigenous) are systematically excluded from. That gets the white and Asian kids into better music schools and affords them more opportunities to get good enough to audition to major orchestras, as well as exposure within the classical-music world so people know who they are. This has the effect of reinforcing a certain racial profile for classical musicians.
The solution to this problem has been known since the initial civil rights movement in the USA at least: affirmative action. Unfortunately that means denying really talented white and Asian musicians orchestra seats, so that talented people of other communities have a shot at the levels of achievement and recognition whites have taken for granted. But ultimately, it's for the greater good.