Probably the same phenomenon as when you first start a relationship or a job everything is wonderful because you just haven't had any negative reference experiences with the said entity yet. Then over time they accumulate and your view matures to one of "it's alright/not bad"

I feel like lately there's been more politics, in terms of news articles as well as comments along the lines of "boo Google" or "boo Facebook", and less new software, people announcing their personal projects with Show HN, interesting comp sci concepts, and that sort of thing.

A good example is this: https://news.ycombinator.com/item?id=19140862

I don't remember seeing that kind of politics on HN in the past.

I started about 4 years ago. While I haven't really noticed much of a decline in comment quality, I think I have noticed a trend towards articles from large mainstream publications making it to the front page. Having said that, the front page as I write this is full of TechCrunch, so it is very possible this is confirmation bias ;-)

Similarly long-time HN user checking in. I think there's still a great amount of quality here, particularly posted material, but I have seen an uptick in the number of junk comments. I'm including comments that say something but are really saying nothing substantive, are blatantly reflexive, or lack depth of thought. Ad hominem and such are indeed still rare here, thankfully.

People often react negatively to change in what they hold dear. It could just be that they all started using these communities, loved the experience at that time, the experience changed, and then they feel the "community" (not their experience) "declined over time." Might just be an instance of that more general tendency.

I won’t join any club that would have me as a member.