IPv6 is here
IPv6 is here. Any business ISP can get you IPv6 connectivity. Many residential ISPs do it by default (but granted not all).
There is much gear that supports IPv6 natively.
What doesn't do IPv6? People. Especially Enterprise/Business Techs.
That is the number one factor. They see no need. They don't bother learning. They don't bother doing. "I don't need it, I don't want it, I don't use it." Stick their head in the sand, no problems here, no need to do anything.
Just about everyone on their smart phone has fully IPv6 connectivity right now.
My home ISP does IPv6. My mom's home ISP does IPv6, and her computer is fully IPv6 connected without her knowledge.
But in 99% of the enterprise businesses I deal with, even though they could enable IPv6 on their firewall and do it, they do not. They see no need, so they don't enable it.
So ISPs have to go to extraordinary measures, like enabling CGNAT. I do not know how much time I've spent dealing with CGNAT issues. Constant breakage. Constantly dealing with slow downs, and all the rate limiting they have to do on their gateways. I tell the customer to get away from the ISP that has to do CGNAT. They don't. I tell them lets try IPv6, and see if all the content you want can be gotten natively. They don't.
I think the only event that will force enterprise adoption of IPv6 is if Facebook or Slack went IPv6 only. That might make the people learn quickly.
Why would anybody believe that a different protocol than IPv6 that will take another 20 years to adopt would do any better? Anything that makes people change what they are doing is not going to be adopted unless it is done for them.