I read a lot of amateur litrpg, prog fantasy and cultivation stories on royalroad.com

I would guess I've actually tried to read more AI written stuff while checking out new stories than a lot of people in this thread.

In practice what I discovered is, AI spends a lot of words to say very little, its prose is quite annoying most of the time. It often makes mistakes in terms of continuity as the story continues.

Now both of those might be corrected with skilled enough use, but the real problem is it doesn't actually understand what makes a story (within a particular genre) "good" and I suspect to actually do that you need to seriously think about and practice writing itself. The process of doing it, is what makes you understand what it is you enjoyed about a genre in the first place and how to write your own.

Genres aren't static, often what readers want is an evolved version of what they've loved reading before, to repeat a piece of Thai wisdom, they want "same same but different" where LLM's will basically give you "same same".