Social media, at it's core, glorifies groupthink, rewarding you handsomely with stars and likes when you say the right thing. In time, you start thinking of what you should be saying, and then you start wondering what you should be posting so that you're perceived as a certain type of person. And when you start down that path, it feels like you become a bit more intellectually subservient. If your concern is always how to please people, how can you be expected to explore heresies? How can you plumb the depths of the unknown to explore and discover things when you concern yourself with safety?
The immediacy of the medium rewards snark and off-the-cuff remarks instead of analysis, insight, and distance. It incentivizes heated discussion (as it garners more pageviews!) and cheap, "me too" posts. It generates a fear of missing out, which is used to manipulate visitors into consuming more and more content for less and less value, exactly like any addictive substance.