I would have quit Facebook years ago, apart from the need for Messenger and the Events system. Sure, people you knew years ago might be on Facebook, but people you currently know are also there, and it's often the easiest way to coordinate an event or get in contact with people, because they actually bother to check it.
I basically haven't used the feed part of Facebook in years, and I am happy to stay away.
If a decentralized social network like Mastodon can start supporting event planning, it might have a chance to gain ground against Facebook. That's really Facebook's only killer feature and unique value right now, IMHO.
I basically haven't used the feed part of Facebook in years, and I am happy to stay away.