It certainly makes it harder to discover human authors, because stores are flooded with plausible but terrible books from morons using LLMs to generate text modelled on other books that are doing well. I don't think that is 'displacing' human authors though, which implies replacing with equivalents?

I'd say it has displaced people like photographers and illustrators more, as businesses are willing to use free generation to replace illustrations/decoration that they didn't value very much in the first place, and are more forgiving of the slop that LLMs produce (you see this in low-end advertising a lot now).

Strange that they are being used to replace many of the things we value in life with low-quality imitations of human work.