I like how you're talking about it like it's some abstract underground BBS style system that requires a modem, ISDN line installed, custom software running on a unix subsystem
I mean I found https://fosstodon.org/home signed up, clicked on local, liked posts, followed people, now I get a stream of posts to my home feed every day
Maybe your everyday facebook user might struggle with the idea of signing up to a site and interacting with it but I'm just not seeing why anyone who can sign up to discord or reddit would struggle with it