My twenty-something friends and I used facebook extensively to run all aspects of our social lives, but now we exclusively use it for messaging and event planning. Nobody reads posts, comments, or notifications unless it has to do with an event.
A few of us have been dropping off and now we're starting to use chat programs (groupme, now Discord) to socialize.
I have to stay on to keep track of goings on in my amateur radio hobby, which as you'd expect is chock full of old men, a majority of which are on Facebook. I think the generational lag has finally caught up to them.