The ISPs still haven't adopted it after 25 years.
ISPs are a massive monopoly in the USA. IPV6 can't be adopted by software until a sufficient number of the backbone works. I've heard that "the backbone is all working for ipv6". Um, is comcast? Wasn't last time I had comcast.
If the ISP monopolies aren't 100% ipv6 (and you see lots of comments here that ipv6 support in ISPs is still "substandard") and convenient, then you can't blame the software people.
Look at your success story in mobile (which is behind a huge NAT to translate things to the "real" internet by the way). How did that work? Oh, you probably wrangled the three or four mobile companies into a room and got them to agree on protocols. Wow, success.
This needs to happen for the rest of ISPs. The fact it hasn't isn't a software issue, it is a governance issue. The failure is in the governance, the outreach with the real policy hammers like the FCC and ISP monopolies.
The governance has failed. It's been failing about 15 years longer than it should. FIFTEEN YEARS OF FAILURE!
Stop blaming reticent programmers, because IPV4 networking is still much much much easier than ipv6 in software, and IPV4 networking SUCKS between NATs and bridges and internal/external IPs and port mappings and what's-my-ip-on-the-other-end and dynamic DNS. Ohmygod it sucks. And ipv6 is worse than that!
Stop blaming the software people. IPV6 governance and outreach failed. Failed failed failed failed.
I don't want ipv6 to fail. I WANT STATIC IPs! EVERY PROGRAMMER WANTS STATIC IPS!
Get the ISPs and FCC in a room. Get google and microsoft and whoever else you need to lean on them. Get Amazon and google and microsoft IAAS into a room (hm, look, the same companies basically) and lean on them to support ipv6.