"Most sites" have no reason to do age verification.
It's obvious that people are arguing about this without actually saying what their personal interest is.
Are this many people afraid they won't be able to get their discord porn channels because mom won't let them borrow her credit card?
The non-porn situations all involve privacy-raping social media that already knows more about their users than the users know about themselves.
"The gubermint is going to find out I exist!" doesn't seem like an honest argument to me. What are people really worried about? And why do them perceive there being value in arguing about it dishonestly?
If it's just an anonymous age flag, why can't open source clients just include support for it, even if they're not required to be this law? If they can verify it, it's something beyond an age flag, and I'll be happy to be left out and "blocked." Like sites that don't work with ad-blockers. So? Byeeeeeeeeeeeeeee. "But we might be left out of the next round of enshitification!" OK? This is bad why?