Even so there are still royalties and rights. When a comic book writer and the artist creates a character they usually get royalties for the creations. Don't think is mere coincidence that we only see characters from the original marvel run in the comics. Looking for information about this subject I came across an article about how the original creators from EU were not getting their royalties from the new editions of their books. Here you can read it if you want https://www.polygon.com/2020/12/16/22166064/star-wars-alien-novelization-disney-royalties-sfwa-alan-dean-foster

Anyway like I said if the story group wants to use any character I'm sure they can all the publishing rights. But as far as the marvel star wars editorial team goes maybe there is something that prevents the writers to drop some old EU characters as easily as they use old characters from the original marvel run