They are social networks not social media, social media is when you scream in a void and the void screams back.

The latrinalia of our age if you will.

I wouldn't call the old stuff social networks. What made social networks a new thing was the social graph of connections becoming the information architecture of the content rather than topics. You found stuff (or it found you) by person rather than subject.

Usenet was topic based (eg reddit seems closest these days), mail lists were usually topic based, forums were organised around topics etc.