"keep in touch with family" can be subsumed by chat apps. But for discussion groups and special interests, facebook is still the most accessible site to run (small) groups in, or am I mistaken?
If you have some need to know the people, maybe, but if not, hobbyist subreddits are better for discussion groups and special interests. The only thing I can't see leaving Facebook is some group that requires real-world interaction like a buy nothing group, but there are neighborhood specific platforms popping up that would enable applications like that without having to use Facebook.