I recommend reading The world in which IPv6 was a good design by apenwarr:

https://apenwarr.ca/log/20170810

It has been submitted many times here:

https://hn.algolia.com/?dateRange=all&page=0&prefix=true&que...

You will find at the end that it has received an update of sorts here:

https://tailscale.com/blog/two-internets-both-flakey