Why spend all this energy complaining about v6 not doing something that it did do?
> The later stage of migration should just be that people start using longer addresses given that both ends are v6 and DNS etc supports it then
It seems your only real problem is that you completely missed the early part of the transition. We've been in what you're calling the later stage for twenty or so years now.
It has "IPv4-compatible IPv6 address"es: https://datatracker.ietf.org/doc/html/rfc2373#section-2.5.4, and then a way to get them over networks where not every hop supports v6: https://datatracker.ietf.org/doc/html/rfc2893#section-5. You don't need new DNS or DHCP to use these, or SLAAC. There's no anycast relay. They can go over v4 hops.
Why spend all this energy complaining about v6 not doing something that it did do?
> The later stage of migration should just be that people start using longer addresses given that both ends are v6 and DNS etc supports it then
It seems your only real problem is that you completely missed the early part of the transition. We've been in what you're calling the later stage for twenty or so years now.