I'm getting pretty rambly but I think this is really a crux issue:
Derivative work has generally been fine in art because human artists are fairly transparent and supportive of other artists.
"Wow, I love your landscapes. Who are you inspired by?" is something you can ask a human artist, and likely get a response. This keeps art very transparent. I think what's so bothersome about AI art is that it produces end products (paintings) but nothing else. To me, visual art is much more than just a JPEG you look at. But maybe to other people it's just that? Idk