Building IPv6 autoconf into the protocol was a mistake. DHCPv6 is better.
The problem is that when you autoconf on a local network you usually want more than just a route and basic DNS. Trying to do it in the IP protocol is a bad idea since the IP protocol is intended to almost never change. It belongs in a protocol that's less tightly bound to the IP stack that can be more easily extended like DHCP.
DHCP can also integrate with things like local DNS, while this is much harder to do with IPv6 RA and SLAAC.
SLACC is something that sounded good on paper but doesn't adequately capture the entire problem domain.
IPv6 in general needs to just deprecate all the parts of the protocol that are anything but just making IP addresses larger. Everything else is "second system effect" cruft that tends to impede adoption by adding complexity or adding features in the wrong place in the stack.
The problem is that when you autoconf on a local network you usually want more than just a route and basic DNS. Trying to do it in the IP protocol is a bad idea since the IP protocol is intended to almost never change. It belongs in a protocol that's less tightly bound to the IP stack that can be more easily extended like DHCP.
DHCP can also integrate with things like local DNS, while this is much harder to do with IPv6 RA and SLAAC.
SLACC is something that sounded good on paper but doesn't adequately capture the entire problem domain.
IPv6 in general needs to just deprecate all the parts of the protocol that are anything but just making IP addresses larger. Everything else is "second system effect" cruft that tends to impede adoption by adding complexity or adding features in the wrong place in the stack.