I noticed the same thing. I was on Reddit for a good 12 years and the quality was getting worse for years, but it's really dropped off since May 30. There are noticeably fewer big posts on r/all and there's hardly any new or interesting stuff. It's reposts, Twitter screenshots, stuff from Tiktok and Discord, complaints (think mildlyinfuriating, AITA, Doordash), and rate me requests. And Facebook type things, like "here's what my kids did today." The bright spots in the sea of trash are gone.
Kbin, Lemmy, and Tildes have been filling up with the good stuff I missed from Reddit. A month ago, it was a little slow here, but not anymore.