The question is: if Facebook ceased to exist, what would really be missing?
There's still linked-in for keeping in contact with people you actually happened to work or study with.
There's Meetups (when they can actually take place again...) and people could probably join mailing-lists or forums about topics they are interested in (gardening, pets - whatever).
It doesn't have to be all hosted on the platform of one giant multi-billion mega-corp.
Probably nothing besides making it easier to get traction on a GoFund me. Other than that I recall the internet was running fine pre Facebook.
I wish we could go back to the days of everyone hanging out on AOL IM. No stupid political memes or arguing between friends.