It's same with usenet... you can get the "chat"/discusson part everywhere now (reddit,...), usually with a bit better UI and it doesn't really offer much more than that. Back in the time, it was the best (and well.. the only) thing to have.. now with alternatives, people move elsewhere, and unless you find a niche you're interested in and a community exists on usenet, you won't have much to do there.
There's no organic discussion happening on reddit. Even the TV show subreddits are tightly moderated these days. If you try and 'discuss' in a way that invites genuine criticism and isn't just mindless cheerleading of the product on offer you'll find yourself railroaded off the site in short order, and the political/real-world/location subs are an order of magnitude more controlled.
Replies don’t get lost because the discussion has moved on or the thread is a day old, like they do on HN and Reddit. This enables long-running, structured discussions. There are more usability aspects related to the text editor used, such as editor commands for handling quotes when replying. There are of course the usual(?) forum features of being able to ignore (filter out) specific users, and other features like automatically highlighting/ranking/filtering messages based on other criteria. But the main usability benefits come from per-message read/unread tracking, keyboard navigation, and the compact thread representation.
Note how on HN and Reddit you have threading, but because each message is displayed inline, you see less of a thread at once. You also see only one topic (thread) at once, whereas in a Usenet client you see all recent or currently ongoing threads in the same view as the intra-thread structure. This causes a more shared experience of subscribers of a newsgroup being aware of the current ongoing threads (over days and weeks) than on Reddit and HN. And most importantly, when returning to a discussion thread, on Reddit and HN you don’t see which messages you have already read and which you haven’t, and thus threads die out after a short time, and longer-form discussions are not practical. The experience is profoundly different.
Clearly they ignored me as they should.