Truthfully - this isn't really about the kids but much more about projection from adults in society who are feeling too much pressure to be 'on' all the time via their own screens.
The internet and smart devices for most people, especially those in jobs that use any technology, has meant a creep creep creep of jobs into every minute of your life. Always available, always checking messages and emails even when 'not working'. (Increasingly companies don't give work mobile phones - can't imagine why...)
If you're not working - you're researching - things to buy - holidays, DIY projects, houses, food, etc etc
Doing admin - taxes, bills, school stuff
Medical things, appointments, banking
Keeping in touch - emails, WhatsApp, Instagram, Facebook
Hobbies - downloading photographs, listening to books,
News, podcasts, message boards, dating apps
And on top of that you have to exercise (after researching all the best ways), prepare food (after reading about all the latest research), teach your children the million and one things they need to be taught (after reading all the latest research), get them to school, make sure they are clothes, fed and emotionally supported (see above), have sex (after reading all the latest research), maintain romantic relationships (after looking for advice about how best to maintain a relationship online),
I could go on, but you see my point?
Children starting school without the requisite skills is a societal failing - not a parental one - we should have decent safety nets in the form of things like sure start (one of the most successful schemes ever - and the lack of something similar could be seen to be contributing to everything we are seeing happens now) and access to high quality early years health and education for all children.
And the problem we are seeing in education may not be because the children's brains are being rotted by screens and social media but because our education system stinks,they hate it and isn't really fit for the way the world is today - AI is going to kill pretty much all the jobs that most kids are being prepared for - society as we know it is going to change in ways we just cant conceive right now - we owe our children the right to be taught and navigate the online world in the same way we teach them to navigate the real world - and that isn't to ban them from it - but to make sure their access to it is safe and managed and balanced with other things in their lifes.