Calling NAT the original sin is a serious exaggeration. Carrier Grade NAT (CGNAT) is a truly evil concept that restricts the freedoms of the CGNATed users. But regular NAT is fine as long as you can control it. "No one wanting to bother with port forwarding" is largely a matter of shitty UX on the home gateway side and laziness on the side of the operator. Same with UPnP.

If anything, NAT has saved millions of wildly insecure devices running unpatched old Windows versions from getting pwned the second they connect to the open internet.

Yeah NAT is still "every household gets a public IP address". This is a perfectly good foundation for an open Internet. You can still host servers in your home. I did this a lot as a kid and learned a ton from it. It's maybe not super elegant but it works.

Going to a model of "you don't get a public IP address, all traffic must go through servers other people host for you" is what finally kills the open Internet. It's okay enough for cell phones where it's a hack to work around TCP/IP's lack of roaming support, but it should be illegal to deploy as residential Internet.

>If anything, NAT has saved millions of wildly insecure devices running unpatched old Windows versions from getting pwned the second they connect to the open internet.

I don't think NAT being a janky ad hoc firewall does anyone a service. It shields the devices enough to keep the developers oblivious about security, but not enough to stop them from connecting to arbitrary hosts. This perpetuates the humongous botnet ecosystem.

> If anything, NAT has saved millions of wildly insecure devices running unpatched old Windows versions from getting pwned the second they connect to the open internet.

Its definitely the opposite. People started ignoring security because its "natted" anyways, even though NAT was never supposed to be security-critical. Thats what firewalls are for.

>If anything, NAT has saved millions of wildly insecure devices running unpatched old Windows versions from getting pwned the second they connect to the open internet.

This might not be a good thing. Perhaps if there had been no protection for those odious operating systems, they'd have died the horrible deaths they earned decades ago. We should only want to protect things we intend to keep, after all, and none of us wanted to keep that garbage.