The problem with IPv6 is that in today's cloud world majority of web server management falls onto developers. With cloud, docker, kubernets and so on devs no longer have to even think about networking.
Before that devs were able to get their heads around basic concepts of IPv4 networking and it worked.
With IPv6 you again start needing more of a network engineer to get the stuff working properly.
It's why even sites like El Reg haven't converted.
One of the networks I ran in our business a an IPv6 only network and you quickly notice the huge chunks of internet that are missing. One of the most confusing situations is Google with its services and its Android. You can get all Google's online services using IPv6 only. But Android refuses to work in IPv6 only mode. Again this is likely because developers are responsible for it in most parts, not network engineers.
Despite all bad things people say about IPv6 the world is rather nice once you're there. I for once no longer have single person at work asking be about that 192.168.1.15 box