It does not address the network level identity and reachability. There is no default, globally routable mapping where owning a ipv4 automatically gives you an equivalent identity in ipv6 that others can reach without translation infrastructure. The transition mechanisms are not uniform or canonical, and that increases complexity.
6to4 was an attempt at that kind of embedding and I do not think it succeeded?
The original specification of ipv6 did not directly address a translation mechanism? It seemed to rely on, well, everyone will go dual stack and we will shut down the old ipv4 stack. I think it should have addressed that in the beginning and provided the one canonical way of doing it, perhaps with guides on timelines to get the ISP and backbone providers to get on board.
Traffic to 2002:70.94.201.31/48 is tunnelled via 70.94.201.31 with-in an IPv4 packet (encapsulation):
None of this stuff works perfectly, but it’s powering almost every mobile internet connection in the world so I don’t understand what is missing.
ipv6 was standardized in 1995 6to4 was standardized in 2001
6to4 is not used in any meaningful way today.
What was missing was ipv6 should have had 6to4 (but better) in it, in 1995.
Now, I could go on about what is wrong with 6to4, but every new topic is just another surface area for ipv6 proponents to launch another question (I sometimes suspect in bad faith).