As I understand it, most adult content producers aren't actually interested in having minors using their sites. It seems like the easiest thing to do would be to have them add some "Adult Material" flag in their metadata, and let consumers respond as they wish to that tag - whether that's done through browser settings, router nannyware, or whatever.
Is there a technical reason this isn't what's being pushed for? I'm sure there's lobbying and "optics" reasons for not doing this, but is there any practical reason for not pursuing this, or something like it?