It's a very sweeping statement but there's a germ of truth in this.
Younger people in particular seem to have lost some of the capacity for that exuberance which goes with coming of age. The period from the age of about 17 to 30 was, for me, unbridled thrill seeking. I spent my time learning about the world and having fun in a very directionless way. People in the age group now seem far less able to do this.
I think there's a number of factors: life is much more expensive these days, it's much harder than it was to get "good" jobs so they have to be much more driven and focused from a much younger age, there's far more social anxiety and of course people seem to spend a lot of their social time online and go out a lot less.
There's a lot to worry about here; the lack of social contact worries me a lot and I think the fact that its much harder to be exposed to other young people and involves so much more anxiety is a terrible thing which we, as a society, should worry a lot about.
On the other hand, I actually celebrate the fact that young people's social lives revolve so much less around alcohol. It's very fashionable to say that this was an important rite of passage, but honestly I spent about 15 years of my young life in an alcoholic stupor and if I knew then what I know now about alcohol and cancer, I'd have given it a swerve. My generation (Gen X) was raised in a very very permissive way which I think set us up for a lot of physical and mental problems which I'm really seeing to start to play out now.
So it's swings and roundabouts.