This author is seriously suggesting that governments ban children's use of social media, and that can't really be done without completely destroying internet anonymity.
Any policy that actually achieved this, without being trivial to circumvent, would basically need to replicate the great firewall of China.
Doing this in a half-assed way is even worse than not doing anything at all. If you just require ID checks for all users to do age verification, you create a privacy nightmare for the adults. Meanwhile, children will circumvent the restrictions with VPNs, so you need to ban VPNs too. Foreign companies, who have no incentive to play by the rules, will surely capitalize on this, so you also need a comprehensive website blocking system. As they say, there's nothing more dangerous than a teenager with very little money and a lot of time on their hands, so a simple DNS-based block definitely won't suffice, you probably need Chinese-style deep packet inspection and such.
The only middle ground I see here is enforcing this through the App Stores, perhaps with an extra ban on sideloading without a developer certificate, guarded byID checks. Losing the ability to sideload would be a shame, but this is the "worst solution, except for all the others" kind of situation. Sure, this is trivial to circumvent by using the web, but the extra friction required due to web apps being worse than native might be a good enough deterrent.