This is a more complicated problem though. Handheld computing devices are a useful and amazing technology. Pragmatically, we don't want to discourage anyone from taking up empowering technologies at an appropriate time in life.
The problem stems from a dangerous combination of minds that are too young to understand and process highly addictive usage applications, and a toxic involuted culture driven by predatory commercial appetites.
It requires a more delicate programme of digital literacy around why (as a kid) you're not allowed a smartphone, what the dangers are, who the bad guys are, how it can affect you and how to say no.
This is slow to happen for the same reasons that sex education is so poorly handled in many countries; it's awkward, full of inconvenient truths and hypocrisy, and many parents and teachers are confused and conflicted themselves.
There is also the sinister aspect that a quiet alliance of governments and big-tech who dream of cybernetic governance through effectively mandated smartphone use are willing to throw the mental health of multiple generation under a bus to get it. One can only hope the backlash continues to grow and more people connect the dots and start calling out the deeper causes.