I used to think that Reddit was bad in this regard but to be honest it mostly affects the big subreddits, the niche and small ones still have a high quality community. HN became pretty much like the biggest subs on Reddit.
This comment thread is in its own category of low quality discussion.
Negativity bias prevents you from seeing that 95% of the homepage right now is technical/nerdy with a lot of high quality corresponding discussion.
When political/social issues hit the homepage, they often slide off quickly if the corresponding discussion is of low quality (has many downvoted comments).
HN is certainly not perfect but just focusing on the parts you don't like prevents you from seeing the bigger picture.