alt Hacker NewsA lot of it seems to boil down to "IPv6 was too early". Had IPv6 been developed a couple years later DHCP would have been mature, and SLAAC would have never been invented (since DHCPv6 is fairly obvious when you have good experiences with DHCP). Also it would have given all the alternative protocols (especially OSI) time to try (and likely fail) to gain traction, freeing IPv6 from the obligation to cram in all of their features. IPv6 could have picked a much smaller set of features that were proven useful by other protocols, then swoop in as the much simpler upgrade from IPv4 than any of the competitors
A couple of years later ipv6 became unnecessary. A big driver for ipv6 at the time was routers not being able to manage the increasing size of the core routingtable. Then 2 years later betterhardware and routing table compression became available and ipv6 became unnecessary.