> I think this means any solution which involves active parent participation is going to get shunned by a vocal subset.
I don't think that's a fair assessment personally, rather you've missed a key detail that things are significantly more complicated than they used to be, it's not just an 'effort' issue. There is no universal "user is age X" setting that applies to everything everywhere, rather everything has a different system and pretty much all of them are terrible in various different ways.
I'm very tech savvy and I still struggled just to set up a Microsoft/XBox account for my daughter so that we could play some computer games together. Access to all the different age rating settings is spread across something like three different apps and websites and in my experience they don't even all work consistently. That experience is also not dissimilar from the experience with other types of accounts. For people I know who are less tech savvy it honestly doesn't matter how much time they put into it, eventually they give up and turn off age ratings because something isn't work and even if there's a solution it would take them hours to figure out.
Point being, if the existing tools were much better I don't think we would be having this kind of conversation.