I mean, it's ultimately about whatever Hasbro decides doesn't threaten its bottom line. It's publicly traded and doesn't want to annoy people who can make trouble for it on Twitter or Instagram. Most (certainly not all) fans of D&D lean left, so that's who they care about--let's not assign any virtue to what a profit-seeking enterprise is doing. The big difference, I think, is that the D&D fanbase is much smaller and more particular than, say, the MCU fanbase. And from what I can tell, this is now unacceptable to a large enough portion of the fanbase Hasbro won't touch it with a ten-foot pole.
Like the decision to get rid of assassins and half-orcs and change the demons and devils to tanar'ri and baatezu long ago, it's a business decision, and neither you nor I is going to change their minds. You get something like the OGL that unites everyone, you can change stuff. But Dark Sun? That's a fragment of a fragment. And nobody's business model really depends on it, unlike the OGL situation where a lot of indie companies were going to go under. Besides, you can always have whatever themes you want in your home game--nothing to stop you from downloading the A0-4 series and playing them if you like, or making your own version. So I don't think we're going to see a big demand for bringing this stuff back.
Is something lost? Yeah, I agree, something is. The fantasy world (IMHO) feels even more saccharine to me when we strip out all the real nastiness of history. One of the things about the past is that life was a lot cheaper--people died younger, and would have ten kids to get three to survive to adulthood. And, honestly, I hate to let Nazis spoil my fun. I don't see why I have to stop doing something just because some 4chan troll likes it or takes it the wrong way. Yeah, I like to listen to synthwave, I know some fascists like it, f*** 'em. I mean, on a more serious note, look at all the stupid hoops Norse neopagans have to jump through to reassure everyone they're not Nazis.
But one of the things about getting older is you stop believing in progress. The present isn't always going to be the best time period. Sometimes things move in the wrong direction. Sometimes you have to look back in time to find what you really want. If you really feel passionately about it, you can advocate for your point of view (like you're doing) and maybe make content the way you want if you're creatively inclined (and some people just don't have that talent, I probably don't). But it won't be 'official D&D'.