At the moment, my "perfect Hacker News" is Mastodon. A curated feed of people sharing interesting things, and that's it. No viputerative snark, no performative cynicism, no wallowing in conspiracy theory, no flame wars, no race wars, no green accounts shouting slurs and death threats. No lectures whenever someone makes a joke or steps on one of an ever increasing and increasingly pedantic set of guidelines. It's everything I wish Hacker News was. It's
fun. Hacker News hasn't been fun in a long time.
If I had to change one thing about HN, architecturally (since trying to change the culture is a fool's errand) it would be better curation. This would go against one of the design goals of HN, having a "non-fragmented" community where everyone sees the same site and the same content. But I would argue that the community is already fragmented. The size and diversity of the userbase is such that people already experience completely different versions of Hacker News depending on when they arrive and what they follow.
Being able to whitelist or blacklist accounts, domains, keywords, etc and curate one's account would improve the subjective quality of the forum across the board. People who want Hacker News to only be strictly technical and startup content can have that. People who want rough-and-tumble politics and debate can have that. And never the twain should meet.
I really do think there is an interesting design space between Twitter and traditional threaded forums that might make for an interesting experience.
And if I had to change a second thing about HN it would be getting rid of voting/karma, because it clearly isn't serving its intended purpose.