One flaw of the LLMs I've used: they will never give you harsh criticism. While it would be nice to think all my writing is just that good, I know there are no circumstances where someone will ask for feedback and it will say “throw the whole thing out and start again.”
@molly0xfff Most writing that LLMs are trained on is -- by definition -- "average," at best, so my guess is that a "good" writer just isn't going to get hard feedback from an LLM. Possibly the opposite.