I think this may be due in part to people learning how to target Hacker News readers with their article and blog post headlines, so while the front page would look similar, the newer linked content is more fluffy.
I mean, there has to be some explanation like this, because it just seems so clear from regular reading that the quality has gone down. Then again, maybe I'm projecting the decline of comments onto the content.
The fact that HN hasn't been overrun by marketing zombies is why I'm not too worried about its direction. If linkbait titles are the big complaint about submissions, it's a good sign.
I mean, there has to be some explanation like this, because it just seems so clear from regular reading that the quality has gone down. Then again, maybe I'm projecting the decline of comments onto the content.