The reason I use it is that sometimes there's a link posted to something genuinely novel, fascinating, and/or perception-shattering. Likewise, sometimes a comment will be deep, insightful and/or informative on a poorly-known topic. These are what bring me back.
But, most often, the community is prickly, fad-driven, and increasingly conformist.
It's always been a mix. I don't think it's actually gone downhill - I think the metric of quality has changed. The new moderation team has cracked down on overt rudeness and trolling. However, the userbase has shifted - it's larger now and more dominated by employees than entrepreneurs. That leads to a narrowing of opinion. The tech industry has also become much more high-profile, and everyone is hyper-aware of the media criticism of startup culture.
Once upon a time people would express controversial opinions and expect at least a fair hearing - it felt like a friendly gathering of smart friends. Now, it feels like people standing on soapboxes shouting to a hostile crowd. People like Sebastian Marshall (https://news.ycombinator.com/user?id=lionhearted) used to be top posters here, and he's no longer active -- and I doubt he'd go down well with the current crowd. Steady changes in the userbase like that change the vibe in hard-to-define ways, but it's definitely changed.