Earlier quoted context omitted.
No more so than it's isolating them by giving them a curfew, telling them they can't hang out in certain places, not giving them a car, etc. That level of "isolation" seems innocuous at worst to me (even though it may seem like the end of the world to the kids).
Then you are either older, lucky or never introspected. I assume lucky for a moment. The problem is less that conversations are more delayed or ad-hoc but more that they can potentially miss out on "group events". And that is where the problem starts. Because they also can't join in on conversations about that event, etc. This means while the rest of the group will frequently have situations where they emotionally bo…
That sounds a lot like when kids say "you just don't understand!" to parents restricting their activities.
The reality is that the parents usually understand fully, but also understand other aspects that the kids don't yet.
> that they can potentially miss out on "group events".
I doubt this is a common or inevitable consequence. First, kids spend a great deal of time in person with their peers at school. Even if something is only planned online, they can still get the details by asking in person. Second, they can use a home computer to do that stuff. A phone isn't mandatory.
> not having a phone also means e.g. not having a camera
If that's important to a particular child, give them a camera. They do still exist.
> it's better to control it in a careful and reasonable way.
I agree. But you can't really do that if they have a smartphone. You can do that if they have to use a computer at home to go online.
I fully understand that kids will consider the lack of a smartphone to be essentially social suicide. They'll feel like it's an existential problem. But it's not. Good parenting often requires parents to do things that kids think are abusive, but are actually necessary to give them the best shot possible at having a good, healthy adult life. One of the main jobs of a parent is to gradually introduce children to reality. Emphasis on "gradually".