Those threads have lots of comments that are both obviously LLM-generated and also flagged by users (e.g. https://news.ycombinator.com/item?id=48262928 ) So if anything, the spam filter is still not strict enough.

And if a newbie's not-particularly-noteworthy comments are only visible to people with showdead on, is that really so bad? If they keep lurking and occasionally posting, at some point they'll say something interesting enough that people will vouch for the dead comment. That would probably actually lead to a more pleasant first interaction than getting downvoted for a low-effort reply.