I'd counter that AI usually writes way better than typical person, definitely way better than any commenters here (myself included).

What's jarring about AI content is seeing the mastery of English applied in mundane contexts, where people are used to see more basic, pedestrian language.

(That, and overuse of patterns, which is more of an artifact of how people use LLMs - specifically that 90%+ of the AI output you see is the first response to the prompt in a fresh session. For AI, each time is the first time it's using this pattern, for user it's the 10th time they saw it within the span of an hour.)