Same here. I've begun actively searching for communities forums, lemmy, etc that make me want to participate outside of lurking.
Your point about the depth of content/conversations is so true. The number of times you'd see the same post over and over again. Then dive into the comments for the top comments to be highly predictable copypasta or "unpopular" opinions that were actually super common made browsing very unenjoyable.
I think you're going to know by one metric. Quality of content over the next ~3 - 6 months. Whether subs stay or go is one thing, that's been part of Reddit for the 12 years I used it. What would get folks to leave is when the communities they are interested in aren't supplying content.
So if you lose some lurkers, that's not gonna matter because they didn't post anyways. If you start losing power users, who regularly feed your community content, what's going to drive you to stick around? If you ask me, I think the fact we are even having this conversation means Reddit is losing in this equation.
I haven't bought any new ones in the past 3 years. But I've abused quite a few and never had issues. High drops, spills etc. Could it be the model? (Not that it makes it any better)