I agree. If AI gets to the point where it can quickly generate endless amounts of novels, TV shows, movies and whatever, the monetary value of such output quickly approaches zero. I can see people having fun generating their own stories with AI, but not paying for generic stuff done by others. It's not even that different from current situation, where there are way more genuine human content creators than demand. Only few succeed, with AI generated content it's going to be even smaller percentage.
Authenticity will become a selling point itself. People will pay more for TV shows with real actors, just like they pay lots for paintings of famous artists, and very little for printed copies that look just like the original. The interesting question is how something will be certified as "real" so that consumers can verify it.