Parents are massively on board.

And they are probably moving to a system where you need to link your device with a government issued cryptographic ID (i.e. passport) using zero knowledge proofs. With a system that ensures an identity can only be installed on one device at a time.

This means a parent would have to give up all social media accounts and chat apps on their own phone, in order to give their identity to their kids.

I use at least 4 different devices on a daily basis, sometimes more. Forfeiting access to things deemed not for children, or I want connected to my ID like banking or prescription renewal, on any one of them because my id can only be on one device, is not an acceptable solution. My phone and gaming machine need equal access to content some would object to others (especially children) interacting with, while my personal and work laptops have hard needs for me being able to prove my identity. And backup devices should any one of the systems I rely on fail need to be able to come up and running in no more time than it takes to get a replacement from the store.

The parents could also check their kids phones and ground them if they find them using social networks.

The parents don't actually need their adult, childless neighbors to show their IDs to protect their kids, but it seems we're going down that exact path.