alt Hacker NewsLLM speak is of "higher" "quality" to a superficial inspection because it uses big words in a grammatically correct way.
It is worse because it fails to communicate information well. When I say it can barely speak English, I mean that it produces sentences which are incomprehensible on the first few reads. I have never found the median literate native speaker to be so difficult to understand, partly because they use a limited vocabulary and avoid waffle.
It can barely speak English in a new and exciting way, one unlike all the previous humans who could barely speak English.
I don't think the claim will bear out that LLM-generated text fares more poorly on comprehensibility tests than those of the median literate speaker. I understand the aesthetic arguments against it, and largely agree, but the technical argument you're making here is almost certainly and starkly false.
Most people write quite badly!