I think Reddit quality has been declining for some time.
There are two factors at work I believe. One, once something goes mainstream, you get a much broader set of the population on the platform, and much like real life, the idiots seem to be louder.
More importantly though, updates to the platform deprioritized serious conversation in favor of mindless scrolling. Look at the new website, or at the official app. They are not conducive to in-depth conversation. They keep trying to distract you with posts from other communities that you don't even subscribe to, the goal is obviously to get you to keep clicking clicking clicking rather than spending a bunch of time on one page composing a well thought out reply.
And that shows. Really high quality in-depth conversations on issues of importance used to be far more common for me on Reddit. Today they are much less frequent, fewer people seem interested in real discussion or debate. And there's much more of the attitude of 'you disagree with me there for you're wrong fuck you'.
I think the recent protest and beginning of migration are going to make that even more prevalent. I think many of the smarter people who enjoy in-depth discussion and post quality comments are going to migrate to Lemmy or Kbin leaving Reddit full of idiots. I think that will actually be good for Reddit as a company, at least in the short-term, because idiots don't use ad blockers and they install the official app without thinking. It is of course killing their golden goose, but their actions suggest they have decided they prefer to do without that goose's continued services.