I also read for plot/story/character, and frankly, a lot of writers suffer on that front.
Badly written stories can be very successful. Project Hail Mary has (far as I could get into it) terribly bland writing and a cardboard protagonist (and scenery, and everything). Harry Potter, especially at the beginning, wasn't that well written, either (though granted not as bad as Project Hail Mary). I'm sure there are a lot more examples.
In that respect, even if you feel that AI isn't that great at writing, it probably surpasses many successful writers. It is already better-than-human in some respects for a subset of writers, perhaps even the majority of writers, just like it's better-than-human in most other respects. It's always worth remembering that about half the population has below-average IQ. :) Comparing the AI to your most beloved authors (especially those who can't, for obvious reasons, publish new books) only says about AI that it doesn't (far as you know) surpass the best of the best.
Also, I assume that you haven't worked with AI for writing. Its entire point is that it can understand context and your guidelines. The other thing is that AI isn't the end all, just like an editor isn't. As a writer you can certainly decide not to listen to what the AI (or the editor) suggests. As a writer before AI, you'd have gone to a critique group, passed your book by a trusted first reader, and the like. A book typically gets suggestions from a lot of people, and you'd be a bad author if you took every suggestion, and a good one if you understand that a suggestion means that there's a problem that you need to solve. The AI is an addition or replacement for some of these people.
LLMs are good for writing, like they are good for progamming. You just have to use them as a tool. If you use them to do your entire work for you, you will get something very mediocre. If you use them to do a lot of work for you and oversee them, you could get some really nice things done.