IPv4 addresses are in fact a subspace of IPv6 (that's NAT64). They were not by fiat declared invalid. The actual thing I think you're complaining about - the necessity for NAT64 at all - is unavoidable, because you need a NAT/protocol-translation layer for packets to actually move between the new address space and the old one.
SLAAC-by-default is not, in my experience implementing IT automation, an actual barrier for adopters. You have a router sending out RS instead of a DHCP server, to an admin this is not a meaningful change.
SLAAC-by-default is not, in my experience implementing IT automation, an actual barrier for adopters. You have a router sending out RS instead of a DHCP server, to an admin this is not a meaningful change.