One anecdotal chime in: I dropped the Zuck for a year and gradually realised that my city runs all its cultural events through Facebook - unless you know or someone invites you, that was pretty much it.
I think I did miss out on meeting new people or seeing old friends by chance, simply because I didn’t know to turn up somewhere for a gig or whatever - and the old addage has some truth imo; often you just need to be in the right place at the right time for things to happen.