I wonder if there's a way to test this hypothesis. Does content being freely reproducible with minor modification increase the demand for content creators since new content is more valuable than the existing that can be copied.

I'd guess that since AI can fair-useify a work faster than any human, that fair-use reviewers, compilers/collagers, re-imaginers, etc content creators will be devalued.

However, AIs are as yet unable to create work as innovative as humans. Therefore new work should be more valuable since now there is demand from people and AIs for their work. I'm assuming that AI companies pay for the work that they use in some way. Hopefully the aggregation sites continue to compete for content creators.