Nonsense. I’ve written bland prose for a story and AI made it much better by revising it with a prompt such as this: “Make the vocabulary and grammar more sophisticated and add in interesting metaphors. Rewrite it in the style of a successful literary author.”
Etc.
Why don't you post it so we can see how much better the AI made it?
Have you considered that your analysis skills may not be keen enough to detect generic or boring prose?
Is it possible that what is a good result to you is a pity to someone with more developed taste?