On the list of great artists of history, for every white woman you list, I think you must agree that either one of us can list a dozen (and likely *far* more) white men considered to be “great artists”. In other words, the exceptions you listed proved the rule, and sorta leaves that part of your claim by the wayside.
And you barely addressed the relative dearth of nonwhites. After all, America will be majority-minority within a couple decades (and since it’s driven mostly by the disparity in birth rates, that’s a demographic certainty even if we stopped all immigration today). Why, then, do whites in general determine what is or is not quality art among nonwhites? For instance, I’m no fan of hip-hop, but who am I to say what is or is not quality hip-hop? Same thing goes for any kind of art, full stop.
When the movers and shakers and decision-makers of the art world are overwhelmingly white, there will be implicit bias — it’s simply unavoidable. This is NOT an indication of malice on anyone’s part, but a simple fact of human sociology.