I'm sure they do, they may not understand the technical details, but I'm not sure why you think people who make rules or pass laws would think the rules or laws won't be broken or circumvented. It's a law, not some magical contract. If your parents say "no Xbox until you've finished your homework", they're not amazed when they find you on the Xbox 20 minutes later, homework unfinished.

It's been illegal to sell alcohol and porn to minors for decades now, do you think before the internet and VHS it was impossible for kids to find? Do you think the lawmakers back then were somehow baffled that the law they put in place, didn't 100% prevent children from drinking and stiffening their socks?

Governments already have systems to handle citizen IDs. They're not perfect, and fake ones do get created, but they're good enough. All that is needed is to connect that system to a UBI key or other device. Then websites could use cryptographic tools (signatures, ZK-SNARKS, etc) to verify that someone is over 18 without revealing their identity

You take control of what you can take control of. Fake IDs aren't new, bars still need to ask for one. Canadian porn sites need to obey Canadian laws.

Also, our youth is so bad with tech that it doesn't know how to use a computer when it reaches university, the tech genius generation was the late X and the millennials and they're all over 18.