Those were pretty much social sites using text with a tiny bit of media (occasional images).
Social media has a big emphasis on the media part, with video clips and images and so on for starting most of the discussions. Twitter started off mostly text and kind of became social media based on the screenshot I have seen of it.
Vine knew what it was and succeeded in encouraging creativity to fit the format. I kind of missed it, but the best of compilations really show off how entertaining getting right to the punchline can be.