Really interesting article. The only point I'd add is that the Shakespeare/Mozart/etc. issue is slightly more subtle than it sometimes sounds.
It's not as if there was a large pool of both white *and* black, male *and* female 16th century playwrights in the English language or composers in the Classical style, from whom only white men like Shakespeare and Mozart were picked as the best. The population of the pool was very, very, very heavily weighted toward white men in the first place, for reasons both social and demographic.
So maybe in a different and better universe the great composers of the late 18th century *would* have included a black woman, but in the circumstances that actually obtained, it was almost inevitably going to be a white man.
Thus the issue is not so much the choice of "greats" as the historical circumstances that allowed them to become great while preventing others from doing so.
For obvious reasons, it's harder to apply this argument to the present day or the recent past. (It does still obtain, but to a much, much smaller degree.)
There's also the issue of elevating western culture in general over other cultures, but that's a different question. (If we say "Milton was the greatest poet" I think it's understood we mean "in the European traditions" and that we aren't comparing him with poets in Indian or Japanese traditions.)