Earlier quoted context omitted.
Fling it around? There are a shitload of people who maintain networks, like home or small business networks, that aren’t network administrators. Most of those people are not prepared to have their Chinese WiFi cameras, myriad smart appliances, and heck, even home computers easily individually accessible from the internet. It’s an extremely simple concept, no?
Lack of NAT doesn't imply lack of firewall, though. And home routers have firewalls that block inbound connections by default -- including with no-NAT IPv6.
But lots of people want to do things like open up a few ports for a gaming console. You can obviously do it, but the inside network/outside network/poke a hole/simple ip addresses mental model makes it harder for people to just get frustrated and disable it. Of course absolutely nothing is impossible or more difficult from a technical networking perspective using IPv6. People want to learn as little as humanly possible to solve their problems. If the default easiest path is ‘disable the firewall, and suddenly you can use the LAN pvp mode with your 6th grade classmate’ then you better fucking believe that’s exactly what they’re going to do. The “well it’s not really that complicated” perspective is the main reason adoption of user-facing FOSS is lightyears behind commercial options.