I love the “jumped the shark” metaphor, but in the interests of derailing the thread with pedantry, I think that’s the wrong metaphor.
To me, jumping the shark is typified by the creators/stewards of a thing making more and more desperate attempts to cling to relevancy, with no coherence between their attention-grabbing efforts, and with nearly all of them corrupting the thing that made the original show/site popular to begin with.
HN may not be the place it was, but I don’t see the site doing wild things like allowing people to post videos that play on the site.
I really think “Eternal September” describes it: There is a new generation of users that now dominates the culture. Thus, it is no longer what it was, but nevertheless the stewards aren’t trying to recover its lost “glory” with stunts.
To me, it feels like a pub that used to be a cloth-cap and sandwiches place, but as the neighbourhood around it gentrified, it evolved to serve a wider menu. But it’s still a pub, it’s not like they pulled out the darts boards and replaced them with a DJ and dance floor.
Reddit, on the other hand... Reddit is throwing stuff at the wall incoherently.
I've seen lobste.rs over the years but never saw it as much outside of "niche HN". But honestly, taking an objective look at the topics on the front page of HN that I care about compared to the front page of lobste.rs that I care about, HN has more noise. Any lobste.rs users want to send me an invite? Email is in my profile.