Movies and TV shows are naturally biased towards social relationships and friendships because it's hard to present a first person point of view. Yet I assume that's where the future of entertainment lies, in first person virtual reality. Peep Show with David Mitchell and Robert Webb is the only exception I can recall but the humour there is fairly dark and nihilistic so it's hardly an endorsement for solitude (besides, they're flatmates). A counterexample from literature I can recall is Robinson Crusoe, who is alone on the island for the first time in his life but not lonely because of a new-found relationship with God.

Reminds me how people felt in the 70s with the wave of ideal tv shows where everything was clean, neat and nice. A lot of people liked shows such as Married with children because it was a show depicting flawed characters and families.

This I agree with, but it was not in the book (I might add a bit about it in my own comments). Thanks for suggesting this: the author says that lonely people have unrealistic expectations about human relationships but he does not mention that movies, tv, novels and comics could have intensified this a lot. So we could probably blame literature/entertainment more than "Social Media"