Read, write, study, paint/draw, think deeply, get drunk, cry, masturbate... there are probably heaps of other solitary activities that I can't think of right now. I'm sure someone who grew up without the internet would know how to keep themselves occupied as they wouldn't know any different.
perhaps some of them were forced to interact with other people more regularly and improved their social problems
interesting that you all think this technology helps you when all it does is insulate you from social contact with actual human beings