Without the daily "forced" interactions with people of diverse backgrounds and intelligence levels that come naturally through proximity, and with all communication centralized and mediated by something that allows you to easily (even transparently) avoid challenging viewpoints, small wonder that society becomes segregated and unstable.
Really, I think the solution is small, walkable, community-oriented towns, preferably alongside the abolition of cars. Solve that, and nobody will care about "social media".
So increased social media use is definitely a symptom of broader disconnection in our societies, but it's also helping that disconnection along quite happily.