Cool. Then don't use LLMs and keep waiting for that prophesied "model collapse" to happen. See how that works out for you.
1) LLM content can at best be as good as the source material it was trained on. That's the upper bound. "Out of distribution" output of LLMs is mostly unusable.
2) LLM-generated content increasingly drowns out original content, online and elsewhere.
This spells "monotonically decreasing content quality" to me.