havard
Adventurer
The old settings for the new generations are too "generic". We are talking about a fandom too used to lots of fantasy MMOs. Even a famous franchise as Blizzard's Diablo suffers the end of its old days of glory. At least Dark Sun could mark the difference.
WotC is not so interested into to sell a product for nostalgic collectors, but to attract new players/consumers. The settings what return should offer something Forgotten Realms couldn't.
Look at the most successful fan franchise today: The Marvel Cinematic Universe.
Did they stop using Iron Man because some of his stories were seen as "problematic"? Did they stop using Captain America because he was seen as too generic and old fashioned? Did they decide never to use Man Thing or Ego The Living Planet because they were too obscure?
The D&D worlds are WotC's Marvel Characters. Potentially they could generate tons of wealth for the company. They could create separate "skins" on DNDBeyond depending on which setting you are using. Treat them as Harry Potter Houses or Team Jacob vs. Team vs. Team Edward from Twilight.
If they were smart, they would bring every setting back. But they have to make them good. At this point, how many people work as permanent D&D staff?