Sorry, I think you're being short sighted here.
When I was a kid, I spent a lot of time rebuilding custom kernels and installing Puppy, DSL and other niche small operating systems on whatever random bits of hardware I could come across. I assume a lot of other HN users did the same. My parents would have had no opportunity to set the flag, meaning everywhere would have to assume default locked/blocked.
> This, as noted above, requires that services respect the flag, which they do not universally do today. That requires legislation, something that will be a part of any workable solution.
This is advocating for a variety of closed internet that is legally locked by default and would require a level of legal and international cooperation that would never happen. I'd argue that the resulting network isn't the Web any more.