I'm not sure about that comparison. For news and television your analogues of blogs and YouTube overcome a distribution bottleneck. Books have for a long time had a low barrier to entry for distribution and that fell further with the internet. There are mountains of amateur fiction and fanfiction online, requiring only an internet-connected device to produce and consume.

LLM-written fiction as explored in the study is generally not published at all. It's treated more like an externalized imagination, a loop of general ideas fed into and expanded on or filled in by the machine with statistical averages. It more closely resembles a sandbox game in my view, a type of media distinct from anything before it in form, and even more distinct in function in that media is generally understood to be a vector of communication between people, and this is instead highly individual.

Actually, it might be closer to say this is similar to a child playing pretend alone with their toys, except perhaps a bit less challenging in that creative roadblocks or narrative building is instantly abdicatable to the machine.