That would feel authoritarian to most, and this is what's happening here.
And on the business, it's a huge cost, so small niche forums and others might just have to close.
The issue is really people talking over each other. You either care about the above or not. If you do, it has nothing to do with children.
If they could find a non invasive way to perform age verification, that's free to the website, there wouldn't be a debate.