Look, I'm not trying to paint the picture that the problems aren't technically solvable; the fact that it kind of is is the part that makes this discussion so durable.

I admit that PIN verification would make it harder to bypass the system, though to be honest with you, I think it's also not really hard to realize that some kids will still manage to figure out their parent's PIN numbers, which they will likely re-use for their bank cards and a bunch of other shit, because most people don't really want to have to come up with 10 different PIN numbers, and we all kinda get the idea that PIN numbers aren't really that secure in the first place. Adding a PIN number requirement is probably a wise idea, but it does make the system a bit more of a PITA for everyone as people will inevitably forget their PIN and need to reset it or what have you. And I reckon that's basically how each countermeasure for problems of these systems go, each one just adds a little bit more pain depending on how hell bent you are on making it work. (I think the PIN number is good enough for trying to prevent someone for stealing your identity with your ID card to an extent, but not as good against people you live with misusing your ID card.)

Of course, you could keep going. You could try to come up with counter-measures to discourage someone from re-using their ID card for other people, and probably at least limit the impact of some of these issues to make the system basically work.

Even if you really do concoct the perfect solution for one country, you then have to make sure this problem gets solved correctly in every individual federal government, and then anyone who wants to offer adult content online has to individually handle identity verification across all countries that require it.

Meanwhile, we already have a system where essentially only adults can buy devices to connect to the Internet, and Internet service plans. You can't even get a debit card in the U.S. without being at least 18 years of age.

The 'bank <-> majority' solution was one I was favorable of... until we were recently reminded with Steam / Itch how the payments system does engage in extra-legal censorship.

We can fix the extra-legal censorship problem. Hell, it might've already happened in the U.S. possibly, because of Donald Trump's "Fair Banking" executive order; I know it couldn't have been the intent, but as written it sure sounds like it unambiguously makes it illegal to deny banking access for legal activity, and sounds like it might even apply to payment processing. I guess the plan after that is probably to strongly regulate adult content as part of Project 2025, but still, it does show that we could actually regulate payment processing such that you can't just claim harm to brand image and block of legitimate customers. I especially agree with this if we're going to do nothing about the massive obvious monopolies in the space.