When I saw your title, I thought this would be going in an entirely different direction. This would be the tendency of older means of online many-to-many mass communication to cease to be considered social media. In particular, blog aggregation sites like LiveJournal and its clones were called "social media" when I began using one. Later I encountered numerous surveys which asked if I was on social media, and followed up with a list of 4 or 5 choices. Those sites were never on the list. All the ones that were on the list were more recent and, importantly, had some "algorithm" that chose what I would get to see, other than the simple rules like "give me everything by this set of people, in order by time posted". I.e. if I could count on seeing a particular post, it wasn't called "social media". By that logic, Facebook, Twitter, Nextdoor, and probably LinkedIn are or have become "social media". Wikipedia talk pages are not; I can arrange to be notified for all postings to a selected list of talk pages. You blog is not social media, and neither is mine. And I'm proud to report that I am "not on social media".