I could see that remixes are partially original. But you're not even doing the remixing; the LLMs are.

Indeed.

Text rather than music, but same argument applies: Based on what I've seen Charlie Stross blog on the topic of why he doesn't self publish/the value-add of a publisher, any creativity on the part of the prompter* of an LLM is analogous to the creativity on the part of a publisher, not on the part of an author.

* at least for users who don't just use AI output to get past writer's block; there's lots of different ways to use AI