IPv6 is not IPv4 with larger addresses and never was. That's BS that has been repeated over the year mostly by people that refuse to work on updating their networking knowledge and often also still talk about network classes because they haven't heard of CIDR. The reason why IPv6 has been fighting since the beginning against stateful (!) NAT is that it breaks one of the core goals of a good network, end to end addressing. I find it amusing to see you ramble about STUN etc. as it is a horrible hack around the problems created by NAT. The reality of the world is that there are a lot of reasons for incoming connections to devices in a home network. Games, VoIP etc. all need hacks to work around the addressability issue.
There are very good reasons why every good network admin should have been thinking about IPv6 support for a long time. It can help massively improve the architecture of the local network by removing all the scarcity reasons that created the mess a lot of larger installations are. Old internal devices are often used as scapegoat, but often are just excuses as dual stack support just continues to work. For some reasons, a lot of naysayers just pretend that it is an all or nothing decision.
We are past the point where major international ISPs have moved towards a native IPv6 core network exactly because it allows them to cut a lot of network layers. CGNAT is expensive for them too and doing it on the edge is more so. At the moment, it is mobile ISPs pushing IPv6 because it provides significant benefits for them.
If you as sysadmin believe that systems that are not directly addressable are safer, you might want to look for a new job. The number of attacks using various devices like phones or printers or end user systems as proxy is so long, that it isn't even funny. If it can connect to the internet, it should be assumed that the internet can connect back.