Disrupt Hacker News! Come help change the way that we Hacker News Hacker News! :)
I'm not near as focused as you are, but I understand your discontent. I have two suggestions.
One, the easy thing (easy as in less work and commitment), which a few others have suggested. Help make HN better, make it what you want. It's probably already closest to what you want, among the alternatives.
Read /newest and upvote good content and good comments. I personally rarely downvote bad comments, I just avert my eyes. I do flag spam, it's like picking up litter. But downvoting is an option, and part of the deal. Just don't "be a downvoter," it will probably make you feel worse, and make reading HN like a burden. Don't carry a cross, just watch the parade. (Worst metaphor you'll read today.)
Write good comments. Respond seriously and helpfully to the occasional lame or hostile comment. Be the change you want to see, and all that.
But mainly, get good at ignoring what you don't like. There's still a lot to like.
Two ... this will take some work and time. You can do it in parallel with HN, or wherever you go from HN. Curate your own discussion group. Look around in your current social, academic and work circle, and talk to a small handful (less than five-ish, more than one), who you think might be interested in discussing what you're interested in. Establish some broad but focused discussion topics.
Set up a mechanism for you all to discuss privately. If you're all local, beer is a great mechanism. Otherwise the easiest and simplest thing would be email, and you should probably stop at that; don't focus on the tools (fun though they are, especially the beer), start discussing as quickly as possible; like, this afternoon. Really, this afternoon. If you like, one of you can maintain a forwarding address, so you don't have to each maintain lists. But you don't need that this afternoon, let that emerge naturally. I've been a member of exactly such a list for ... 15 years? Dayam.
Every once in awhile, invite a new individual in. Do it slowly and deliberately. Don't obsess or agonize over whether someone is right for the group; if you thought of them, they probably are. If they aren't, they'll stop participating. New people will change the dynamics and focus, and that's a good thing. Just do it slowly, not as a focus.
Be generous and engaging with your fellow list members. Accept heat, and let it dissipate quickly. The fewer rules you have, the less they'll be broken.
Over the years, your group might grow to five, or ten, or a hundred, it's up to you.
As you communicate with people you know personally (or online personally), there's a danger that the group might take on some social aspects. You may even become friends with some or all of them. That's a risk that you'll have to take. It's not so bad. :)