I don't know if I'd call it a mass exodus, and I don't know that it directly has anything to do with Lemmy, but there's been a noticeable dip in quality. Fewer posts across many of the front page subreddits, fewer votes, more bot posts, more low effort posts, less discussion in comment sections, lots of deleted comments and accounts... overall there just seems to be a dip in quality.

I was going to delete, but decided to stick around for a while first, to see how things pan out, and I've got to say the mobile site is even worse than expected. I get constant pop ups trying to direct me to download the app, then when I say no the website will auto reload, often sending me back to the top of the page. It's difficult to find and respond to anyone who replies to your comments, and sometimes if you sort by top: today it won't even show any posts. Just... blank. Clicking on a post opens it as a tab that is more like a popup, and closing it resets where you were on the page.

I could keep going but I think that pretty much summarizes what I've noticed. Don't know that it's directly related to a Lemmy "exodus," and I'm still finding my way around here so I can't really say, but reddit as we knew it seems pretty dead.