Where in Europe are you based? I'm seeing the exact same behaviour you're describing here in Germany all over the place, all the time, and I think it's a serious problem.
I live in Koeln (and lived in northern parts of Germany before that) and I just don't see it. There are a couple of people glued to their phones, but the vast majority simply aren't. And this is taking public transportation throughout the day, especially morning and evenings at rush hour. It's far from problematic.
German resident here, around Cologne/Dusseldorf/Bonn. This has not been my observation (Might be due to my social circle bias), unless you are talking about high schoolers. The general population does not seem to have this behaviour.