Derivative works don't change the originals. They are still there. Obviously, if you're a purist, then don't consume any of the "newer" material.

Is the fear that a derivative would some how make the original less successful? or fail itself or reveal some character attributes that you don't like?

Don't people argue that basically all Star Wars movies and recuts post-1983 have basically just served to dilute the brand? I guess it's a bit more murky when you start arguing about the whole expanded universe of novels, video games, TV shows, theme park attractions, and whatever else.

But it does feel different when you invite new creators to step up to the plate and create new chapters in a story and then explicitly elevate those new chapters to the same level of canon as the original. This could even be said to apply to Lucas and the prequel trilogy, since Lucas did not direct Empire or Jedi, so the prequels were being made essentially be a completely different team than the originals (other than him).

All that to say— this could be done, but it would be really important to manage the branding of it. It's not an "LOTR sequel", it's "LOTR Legends — new stories set in Tolkien's beloved world", with the clear implication that canon 0 is LOTR, canon 1 is the Christopher Tolkien-edited works like the Silmarillion, and the "Legends" are canon 2. Anything not associated with the estate is canon 3, and the movies, video games, and TV show are not canon at all.

> Don't people argue that basically all Star Wars movies and recuts post-1983 have basically just served to dilute the brand?

Some of the expanded universe Star Wars is quite good. I personally loved the KOTOR game and the Yuzhaan Vong books while hating all the Disney movies. I suppose the same argument applies to the Silmarillion since it was heavily edited by Tolkien's son.

> Derivative works don't change the originals.

Often repeated as a mantra, but do they actually not?

Classic example: The plummeting of the rewatchability of Game of Thrones Seasons 1-4. Also, Star Wars.

They don't have to, it depends on the reader/viewer. Stephen King says pretty much the same about adaptations of his own work...however badly they've butchered "The Stand" on TV, it hasn't changed the original book.

I feel like this about a lot of derived works - there's tons of novels derived from video games as well, for example. But they all feel like fanfiction.

That said, there was a fantasy series I've read part of where the author himself started writing tons of spinoffs and whatnot; almost like writing fanfiction of their own works.