Whether or not training is decided as fair use, it does seem like it could affect artists and authors.

Many artists don't like how image generators, trained on their original work, allow others to replicate their (formerly) distinctive style, almost instantly, for pennies.

Many authors don't like how language models can enable anyone to effortlessly create a paraphrased versions of the author's books. Plagiarism as a service.

Human artists and writers can (and do) do the same thing, but the smaller scale, slower speed, and higher cost reduces the economic effects.