That was my experience too. Of course, I identified several causes that made things worse, and which were, at the time, unusual. Moving every 2-3 years while growing up didn't help at all, e.g. Funny thing, that seems to have become more common.
So quite possibly teenagers are now less socially apt than they were. I don't know. But there are many reasons why this might well be so.
That said, it's quite possible that computer games render recovery more difficult. (Recovery? But what better word is there?) This doesn't make them the proximate cause. I'd be more willing to blame parents keeping their children locked in their homes "for safety's sake". Or moving around more. Or loss of neighborhood schools. Or... Please note that each one of these "possible causative factors" has it's own separate reasons for happening. So fixing the problem isn't simple, and fixing the problem would only help the next generation, not the current one.