That would be an unlicensed reproduction of the work. You’d need permission from the rights holder to create what is essentially an audiobook recording.

That's not what LLMs typically do, though. Pull up ChatGPT and ask it to recite Harry Potter for you. It'll fail.

Ask it to write a book similar to Harry Potter, and it'll make an attempt at it. But human writers absolutely do read Harry Potter and write similar books, and that's perfectly legal. There have probably been thousands of published books inspired by Lord of the Rings.

Look at how many people get blocked or demonetized for covers of existing songs which may not even be that close to the original. You can't even play a few seconds of the original in many cases, even for fair use and criticism/discussion. This is already in place.

Talking about what is allowed on youtube as if that's what defines what is copyrightable is a bait and switch. Youtube has an extra-judicial copyright system that explicitly favors large media owners so they won't sue youtube again.