I will argue smartphones or any electronic is not the problem. The problem is lazy parents.
My kids all have had phones since before 10 and they're all well adjusted but to be clear I monitor their usage and I check in with my kids regularly.
I cannot hold back society or technology at the fear of my kids being left behind. What I can do is help them navigate both as they grow.
I love how quick we are to lay the blame anywhere but parents.
This is an extremely reactionary take. I hear what you are saying but I draw the line as delusional and irresponsible unless you apply that to pretty much all parents that don't completely smother their children.
We make mistakes as we grow. We lie. We get hurt. Technology is always Pandora's box. I'd argue we have better knowledge of our kids now than we ever used to and stats show the world is safer now than it has ever been.
If you live in fear you will form your decisions from a place of fear.