I think banning facebook/instagram/etc is one of the special cases where it makes more sense to be enforced by the site, because people use these out of mainly peer pressure and network effect. If a majority is kept off, the rest have little use for it regardless of their personal wishes. Heck, I'd reckon most kids don't actually want to use them all that much. Regardless of technical details, giving parents this control will also cause a lot of resentment if most parents don't go along.
replyAs opposed to censoring internet content in general, which does not work because there will always be sites not under your jurisdiction and things like VPNs. I don't support any such censorship measures as a result.
But why not both? I'm coming from a USian perspective here where I don't see much possibility of actual widespread bans of these types of products, rather just a retrenching to what can be supported by regulatory capture.
replyAlso, we're getting the locked down computing devices anyway - mobile phones as they are right now are a sufficient root of trust for parental purposes. So it seems pointless to avoid using that capability (which corpos are happy to continue embracing regardless) but instead put an additional system of control front and center.