Earlier quoted context omitted.
The reddit death spiral is AI, bots, and brigading. I think they've accelerated it by making it easy to make all comments private and by hamstringing moderators. Part of that directly ties back to AI as well. The API limiting has a lot to do with making it hard to scrape reddit for data.
I definitely think that has made it worse, but Reddit was on the downward spiral before LLNs/Bots/etc for years. Keep in mind that ownership changed twice in the years before ChatGPT et al appeared, and the new owners didn't really understand the site.
Stack Overflow's situation, of course, is totally different. It only changed ownership once.