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It's not just you — no one is posting on social media anymore
(www.businessinsider.com)
This is a most excellent place for technology news and articles.
In broad strokes, yeah. I'd even consider older, more traditional forms like forums and IRC/BBS to be proto forms of social media. As long as the internet exists there will be social media, what form it takes is malleable depending on the desires of the userbase at hand.
At that point the operational definition is just "website where you can post stuff"