I've been starting to think this way as well. It feels like we're seeing something similar to the way that mass spam calls drastically changed the way people use the phones to the point where people don't recognize a phone number, they just don't pick up anymore. As the ratio of garbage goes up, people will just slowly stop using the medium.
My semi-crazy prediction is that AI like GPT are going to be the death of large social media sites. I don't think the internet will die, but I think we're going to return to a more local, trust-less internet like we had in the 90s and early 00s, but for a completely different reason.