Here's how to fix IPv6:
Don't do IPv6.
And here's the simple reason why: the IPv6 address space is so huge every device can be assigned its own, easily-tracked fixed IP, which is a bonanza for the techno-fascist Big Data companies.
The very raison d'etre of IPv6 - which is to solve the IPv4 address scarcity problem and do away with all the nasty hacks to get around it - was desirable before surveillance capitalism, when the internet wasn't a dangerous, adversarial place. Now you want as much IPv4 NAT and masquerading as you want, to make tracking you a little bit harder.