I find it amazing how that lack of curiosity about how computers work extends into modern software developers, I guess that the majority of the industry nowadays are people that do things like "bootcamps" and go into it for the money.
I have no need for ipv6, however I wanted to know about it so spent a couple of hours setting myself up with it. I don't bother with the latest fads that last 3 or 4 years and then are replaced by a new fad, but ipv6 has been around long enough that it's clearly not a fad.
IPv6 has been around long enough that it's clearly a failed project. It's been 30 years and it hasn't even breached 50% adoption. It's not even at the hard part yet, which will be the long tail.
You have a very radical definition of "failed". Take your emotions out, and perhaps you would get a more objective evaluation of the technology.
For one, it's very clear that IPv6 has only, truly received global attention after the depletion of IPv4 address space -- someone has already linked the Google IPv6 adoption page, go have a look at it, look at the flat line before 2012. That means we have spent about of 10~15 years of time deploying IPv6, not 30 years, and getting to 50% adoption in such a time period is not what I'd describe as a failure.
Secondly, if you are defining failure as "less than 50% prevalence in 30 years" then HTTPS before 2014 will probably fall under the same category too. (Don't underestimate the age of SSL/TLS.)
Do you consider HTTPS a failure?
Hell just look at SDWAN land and everyone acting like it is the second coming of jesus when it is just a fancy marketed version of technologies that have been available for decades.