Yeah, IMO trademarks are important and should be protected. And publishing full works should have royalties go to the original producer, and this is a case where I think for the lifetime of the artist is fair. Though I do think that the royalties should have a formula rather than being entirely determined by the original producer (to prevent the price from essentially making it not available), though an exclusivity period would be fair, though with a duration of maybe a year or two.

With trademarks, canon can be established, as can standards like "cartoons with the Disney logo won't be porn".

If someone wants to make a series where Luke Skywalker and Jean Luc Picard fly around the galaxy settling Star Wars vs Star Trek debates by explaining Muppets are better than both and then order Darth Vader to massacre everyone that disagrees and the Borg to assimilate the rest, it doesn't harm the originals in any way. Unless it's so much better than no one cares about the originals anymore, but that's just the way competition works.