This is a tough one.
On the one hand, I feel like kids need to grow up understanding the world as it is today not what it was like when we were kids. Smartphones are part of the world today and being proficient in using them / the services you access through them is a useful skill to have. I mean, when I was a kid I liked using computers and there was probably concerns about kids spending too much time on the computer. But longer term I ended up building a career in technology that maybe I wouldn't have had if I didn't use computers when younger, learning how technology works, writing my own computer programs etc. In summary, my use of technology in the home as a kid prepared me for adulthood more than for example some of the lessons I had at school.
On the other hand, I see first hand how kids get addicted to the devices, what's really interesting is how they seem to prefer using a smartphone over watching TV, even if all they are doing is watching video on the smartphone. I think its because it reinforces a short attention span cycle where there is infinite content online rather than having to sit and watch something 'boring' for longer than 20 seconds. One of my personal bugbears is that my wife has let the kids use her phone from a young age and it's sort of become a pacifier like if we are in a restaurant or something she'll use it to stop them acting up but that in itself just reinforces a cycle where they need constant stimulation and haven't learned how to handle 'boredom' properly.
As others have mentioned let's not pretend that smartphones aren't a problem for parents as well as kids. Maybe we should ban smartphones for over 16s, which in turn means that the parents would engage more with their kids instead of handing them an iPad so they can scroll social media in peace.
