Well, maybe. But there are overwhelmingly large numbers of people who want to be in a fandom, and that means being fans of some shared thing. Maybe that shared thing will be AI generated, but it won't be a world of solipsists.
A world without fandom is one without sports. That seems deeply unlikely to me! Anyone can generate personal podcasts with NotebookLM, which people enjoyed for a bit but doesn't seem to have made any impact on actual podcasts at all.