OK, first off, the straight white guys have had dominance for literally hundreds of years so it's time to let other people get a chance get written for. And secondly, there's still tons of stuff out there for the straight white guys. The stuff for other people is, in fact, being written "in addition" to the stuff for the straight white guys. The fact that we're getting equal treatment doesn't mean that you're getting lesser treatment.
And thirdly, nothing is being removed. To go back to Dark Sun, all the older books are still there, slavery and all. You can buy them online. The actual pdf of the original boxed set is on sale for $7 on DM's Guild. It's just that WotC is choosing to not put out anything for it for 5e--like they have chosen to not print new Birthright or Mystara or Council of Wyrms or Nentir Vale for 5e.