Before LLMs came around, it took quite a bit more effort to write something than to read it. So the fact that someone had taken the time to create something was a signal that they thought it was worth that effort, and so it might be worth my (lesser) effort to read it. And even with that filter there was a lot of human-created crap out there.

I value my time. With a LLM, it takes very little effort to create a vast mountain of crap that will take a lot of time and effort to read through. True, it is also possible to use LLMs as a tool while creating things that are not worthless. But the fact that someone has not taken the time to make their thing not sound obviously AI-generated is a strong signal that it will not be worth my time.