Which IPv6 “gratuitious” features (i.e. anything other than the decision to make a breaking change to address formats and accordingly require adapters) would you argue made adoption more difficult?

IPv6 gets a lot of hate for all the bells and whistles, but on closer examination, the only one that really matters is always “it’s a second network and needs me to touch all my hosts and networking stack”.

Don’t like SLAAC? Don’t use it! Want to keep using DHCP instead? Use DHCPv6! Love manual address configuration? Go right ahead! It even makes the addresses much shorter. None of that stuff is essential to IPv6.

In fact, in my view TFA makes a very poor case for a counterfactual IPv4+ world. The only thing it really simplifies is address space assignment.

In my opinion the redesign of IPv6 was perfectly fine. The IPv6 headers are significantly simpler that those of IPv4 and much easier to process at great speed.

There was only 1 mistake, but it was huge and all backwards compatibility problems come from it. The IPv4 32-bit address space should have been included in the IPv6 address space, instead of having 2 separate address spaces.

IPv6 added very few features, but it mostly removed or simplified the IPv4 features that were useless.

Everyone is saying this but... what are the new features, actually? There are a couple of cleanups to the header, removal of fragmentation, and a bunch of things like SLAAC you don't have to use if you don't want to?