The problem IPv6 is solving isn't a problem today, because the problem IPv6 is solving is no longer workable.
People hated NAT because it puts up a basic stateful firewall between endpoints. And we needed that because we don't have enough IPv4 addresses.
IPv6 was to preserve that end to end connectivity, and not have to do all sorts of hacky workarounds like FTP proxies, port forwarding and other such things like STUN. It was also to make IPSec practical and workable.
But how much of that is true now? You don't see FTP proxies anymore - because PASV mode, but also because no one uses FTP anymore. It's either FTPS, or SFTP (ftp secure, which uses TLS over the FTP connection, breaking the gateway, or secure FTP, a protocol working over SSH).
End to end connectivity is broken because no one would consider putting up anything on the Internet without putting it behind a firewall. So all the nasty IPv4 hacks have to be preserved on IPv6.
We've also gone higher on the stack - where a lot of things happen over HTTPS and now we have firewalls that inspect way up the network stack.
The fundamental reason for having IPv6 got broken over a decade ago, and people stopped bothering because it had no benefits over what exists now.
It still has use - it does have a larger address space, but that's the only benefit it added. So it's popular on sites that have so many devices that they exceed the IPv4 private address space.
That's the reason IPv6 isn't the primary protocol, despite being around for over 3 decades now.
In a way, you can see it as the electrification of cars - EV owners are the new IPv6 adopters. We've been running out of oil for about the same amount of time, but we've also been getting better at extracting harder to extract oil (at increased cost - we aren't getting $1/gallon gas anymore despite it not being all that long ago).
Also, IPv6 purists are just nasty to work behind. IPv6 would replace everything you need - no need for DHCP, NAT, etc anymore i IPv6 does it all. Of course, that attitude dismisses why someone might want DHCP, or NAT, and yes, DHCPv6 and NATv6 exist for those reasons, but the purists hated them for existing and for ignoring very real issues for why one might want to have them.
That, and the music and movie industry should be pushing for IPv6 more heavily because it destroys a key argument in the lawsuits - that the person using the IP address is the guilty party. With everything having independent IPv6 addresses, it's far easier to go after the pirates because they're likely the sole user of a computing device with that IP address. Not an entire family behind a single IPv4 address, when you can have every kid's phone having a unique IP so you can sue just the kid.