Given current social and political realities, though, and a series of deeply troubling news stories coming out of facebook, I think it might have lost a very large segment of young people that will never join or return. I watch my 15 yo daughter interact with people online, and she has no interest at all in facebook, and her interest in instragram is waning. Currently, her primary interaction space is discord.
I've heard semi-private chat rooms are what is going to be popular, and I expect that we're going to see that kind of thing in facebook soon. I wish them luck (not really) building a revenue model on it that matches what they currently expect.