My response is -- since when has the market been an independent behemoth?
Dora the Explorer, Dragon Tales, and Sesame Street are truly popular. They have been pushed and supported, and have built a base. They use advertising -- a commercial tactic successful for centuries, to push the market to accept the product.
That's what the Marlboro Man did for cigarettes. And what the "Diamonds are forever" campaign did for diamonds. Promotion was the key to their industries' success.
Now granted, not every promotion works. But if publishers spent the time promoting books that have characters of color the way, for example, they promote a John Grisham novel -- you might not get the Grisham sales, but you would certainly get more notice from the market.
And it's not only the market that matters. Despite all that awareness that J.L. touts, there's still a lot of blindness on the creative end. How many fantasy books are still published that have all white humans while the non-humans sport every shade of the rainbow? How many middle grade and YA books are published which only include white characters?
Yes, there's been change -- and that's to the good. But raising our hands in defeat intoning "We can't get any further because the [dum-dum-DUM] Market won't support it," forgets the most important fact of all. The market is made up of people. Who can be convinced, successfully, that characters of all color are interesting. If someone is willing to invest in the promotion.