The other choices for IPng at least tried to have an actual transition plan that would involve IPv4-only networks connecting to IPng. In fact the IPng criteria requirements outlined there be a straightforward transition plan from IPv4 that was simple and realistic. Then they settled for IPv6 which had no transition plan and still doesn't have one that meets the criteria set forth in the IPng requirements -- to this day.

The selection committee and ngtrans are to blame for not ever coming up with a transition plan that included interoperability with IPv4 as a basic tenet. They've effectively made IPv6 a second class protocol and will probably end up being like this forever.

IPv6 is effectively a waste of time, and that's how it's seen by most enterprise and ISPs. I'm holding out hope for research in future Internet architectures that will hopefully not make the same mistake as IPng and instead come up with actual transition plans with their designs.