I agree, 2007 is closer to the epicenter. However, I also think the shift away from social media and cell phones is rather uncommon. I have had no social media for almost a decade, but we are few and far between.
A main difference between {MySpace, Facebook, Twitter, Instagram, etc.} and {reddit, hn, chronological forums, etc.} is that the former heavily rely on following/friending (i.e, establishing your social network) while the latter do not. Thus, the latter are not "social media" in the sense of media existing in a social network.
Also, I find that when replying to something in the former I'm thinking about the person (I know them, in some sense) and what they said, while in the latter I'm thinking almost exclusively about what they said (I probably don't know the person). The latter lacks that social element.