For me it's indeed around COVID where my habits changed. That deserves more attention indeed. Something about the vibe changed. Could be just me, and could be just a coincidence that is happened around COVID. But it's worth considering.
I don't know if it was me getting older, or caring less about startup scene but I agree, when Meetups started up again it wasn't as fun to stay up late and get together masked up to listen to someone talk about a basic web app or api. The vibes might have come back now that we're not masking, but it's a bigger commitment for me now to go in every week. I also feel like groups put a lot of content upfront to talk about their agenda and org functions when it used to be more of a "you're at the [topic] meeting, here's what we have for you today".
Where I'm from religious observance went down considerably and permanently - it was declining before the pandemic, but it reached a tipping point only in the early 20s.
Apparently everyone was attending mass largely because everyone else was.
I'd be interested to see how the drop correlates with pets. We got a dog during COVID, she acclimated to a house which never has guests. Now she can't handle guests. Shame on us, perhaps, but anyway there it is.