The mere fact that you took the time to compile this lengthy response and have received meaningful responses is evidence enough that HN has not "jumped the shark."

It is a people problem, but I feel the biggest problem is that people are pointing out that there's a problem. Communities evolve; that is, in fact, practically all they do. Perhaps HN isn't the same as it was 2 or 3 years ago, saying that it's worse is a bit of a stretch.

I've yet to find a community where people have meaningful discussions in the comments without some snarky response like, "lol wut"." On HN these comments are self-moderated; those with the karma downvote the meaningless comments and they disappear into the aether.

Simply put, I don't think HN is dying. Rumors of its demise are highly overblown.