There are local chapters of the Society for Creative Anachronism that uses Facebook heavily. The thing is that the use of FB grew out from the in-person community that had formed, and people would rather interact in-person than only through social media. The community already has its own customs and ceremonies for recognition; people there upvote and collect following in an attempt to get the FB algorithm to spread the word for each other (on events and happenings).

When there is an already-existing community like that, I think a dedicated social media platform for that particular community can be beneficial. That platform then does not have to be the social media for everyone.

However, funding (for hosting and maintenance) is still an issue.