Social media presence as in having accounts in your name with you being visible in the profile picture in mainstream sites (Anything Meta, Twitter, Snapchat, Tiktok…). I don’t consider anynounmous accounts on Lemmy, Reddit, Kbin relevant to the scope of this question.
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.
I’ve experienced the same thing. Facebook Marketplace has also largely displaced Craigslist in my area. Though on the whole I’m still glad I deleted my Facebook account.
I host some decent sized gatherings for my extended friend group (20-50 people). The invites are all on Facebook.