On restricting, I really think that's the responsibility of parents. I think the problem here is that Android and iOS don't empower their users (parents) to implement proper parental controls. I imagine apps don't get the access and maybe the parental controls implemented by the OS don't suffice? Maybe because Android and iOS benefit from these kinds of legislation that cement their duopoly.
I agree that none of the current user platforms, i.e. Android, iOS, nor desktop, have adequate parental controls that are easy to use. Parental controls are important but that's not enough. We expect parents to not buy liquor for their kids, and make reasonable efforts to prevent their kids from obtaining it. But we also expect liquor stores to not sell liquor to kids. We should likewise expect that internet content platforms do not deliver inappropriate content to kids.