The purpose of Show HN is to "show something you've made that other people can play with. HN users can try it out, give you feedback, and ask questions in the thread" (
https://news.ycombinator.com/showhn.html)
That isn't possible with many AI generated projects because OP didn't write the code, probably doesn't understand the code and can't discuss the code or their process in creating it (because said process doesn't exist.) There is little if anything of substance to discuss or play with to satisfy intellectual curiosity, and in many cases the projects themselves wouldn't pass muster if written by a human, they're just vibe-coded slop.
There have been exceptions which have done well (ex:https://news.ycombinator.com/item?id=49550375) but in that case AI was used in a specific technical context by someone knowledgeable who definitely wasn't "vibe coding" anything. But again - if a human had done all of that work, it would still have been a worthwhile post.
Show HN can't simply be a place where people post slop and everyone claps at how cool the latest models are. It can't simply be advertising for LLMs.