When I read the title I hoped that EFF was going to do exactly that.

There’s also a way to improve it: Sell “age verification cards” in physical stores. Just like they are verifying that minors aren’t buying alcohol or cigarettes, they can verify that these cards are bought only by grown ups. Sure wouldn’t be perfect but it greatly improves anonymity and especially in paid-for adult services can be used as a payment method so repeat verification will happen for top ups.