Why this illusion, and how, you may ask? I can tell you why and how! It's because people are far more likely to notice the data points they dislike (https://hn.algolia.com/?dateRange=all&page=0&prefix=true&que...). Not only that, but the dislikeables make a stronger impression when you do notice them. This is why people with strong feelings on a topic always feel like the site is going to the dogs—they're unintentionally blotting out the other data.
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Edit: here are more recent examples in case helpful (what can I say, it's a hobby)
The HN crowd is far right - https://news.ycombinator.com/item?id=41370117
libertarian tech bro site - https://news.ycombinator.com/item?id=41674836
a haven for alt-right trolls and hateful abusers - https://news.ycombinator.com/item?id=41799329
HN has also been taken over by fascists - https://news.ycombinator.com/item?id=42059688
techno-libertarian pseudo-intellectual fascists - https://news.ycombinator.com/item?id=42393303
HN has gone way to the authoritarian right - https://news.ycombinator.com/item?id=42066014
tows the line when it comes to techno-fascism - https://news.ycombinator.com/item?id=42781203
Hacker News is pretty much far right when it comes to politics - https://news.ycombinator.com/item?id=42618465
I've got just as many pointing the other way, of course, but the valuable examples point opposite to the illusion. That is, if I were replying to one of these (^^^^) commenters, I'd point them to your post instead!
See also
https://news.ycombinator.com/item?id=13110004 (Dec 2016)
https://news.ycombinator.com/item?id=25391526 (Dec 2020)
https://hn.algolia.com/?dateRange=all&page=0&prefix=true&que...