God, IPv6 got the shaft hard. People complain that it's too complex and that it solves too many problems at once, but that's because they've become used to the ancient stack of random protocols that make IPv4 work. There are also a lot of people who have it out for IPv6 because their ISPs aren't handing out static addresses, somehow equating IPv6's problems with the shittiness of their ISP.

It's not widely implemented because hardware support is lagging behind (Ubiquity being a notorious example in the prosumer space), hardware support isn't being developed because it's not rolled out widely, software support is lacking because of a lack of rollout which is then used as an excuse not to roll out IPv6.

I bet that if people learned IPv6 before they learned about IPv4 the conclusion would be that IPv4 is a mess. In my opinion, DHCP is a stupid protocol for assigning addresses that shouldn't have been necessary, but we've managed to staple some kind of management ideals on top of it (as if someone couldn't just set a static IP on their device) and using SLAAC feels like giving up control for some. Imagine trying to convince people that they have to set up a USBCP server on either their computer or their flash drive to make USB work without address conflicts, or to make Bluetooth work, they'll laugh at you and ask why that stuff isn't done automatically by the underlying protocols instead. DHCP is useful for many other settings, but address negotiation should've never been a problem it needed to solve in the first place.

We've accepted NAT as a fact of life because of ISPs being stingy to hand out addresses years ago when multiple devices started appearing in home networks and now people treat it like some kind of firewall (which it usually isn't!) or absolute necessity because they can't imagine something else.

Ask any console player about what type of NAT they have (NAT type 0? Type 1? Type 2? open? moderate? strict? I've never been able to figute out what these classifications even mean on a technical level!) and they'll shudder with flashbacks of getting basic connections to work with their crappy ISP router. This should never have been a problem, but everyone kept dragging their feet and eventually we decided to accept this mess.

I think part of the reason is that many schools still only teach IPv4 in their networking classes, so when people encounter IPv6 in the real world they're scared and confused by concepts, protocols and mechanisms they were never prepared or trained for.