A few notes on the timeline.

The IETF has a two-level standards system consisting of "Proposed Standard" and "Internet Standard". IPv6 was first published as "Proposed Standard" in 1998 and finally transitioned to Internet Standard in 2017. Although officially Proposed Standards are supposed to be treated as "immature specifications", as a practical matter, people routinely deploy on them. Whether an RFC is advanced to Internet Standard is less a question of whether it is mature than whether the editors and/or WG bother to advance it. Here are a number of examples of widely deployed protocols that never advanced beyond Proposed (1) all versions of TLS (2) HTTP/2 (3) SIP (4) QUIC.

I think choosing 2012 as your start date is pretty generous. Proponents of IPv6 were telling people to start deploying long before that. In fact, the IETF sunsetv4 WG, dedicated to sunsetting IPv4, was formed in 2012 several months before World IPv6 launch day. Arguably, World IPv6 Launch Day was a reaction to the failure of v6 to get large-scale organic deployment 12ish years in.

> If you pass a IPv4v2 packet it will not be routed. You'll need to replace all networking equipment to support IPv4v2...which is what we've done/currently doing w.r.t. IPv6

That was never the difficult part. Mosr corr routers and expensive gear supported ipv6 many years ago.

> We're at over 50% deployment in the US. Again, it's closer to 10 years.

That means almost nothing. Even if you have 100% deployment, it is more expensive to maintain v6 by server admins,developers and consumers alike, especially in the not so rich countries. It just adds more maintenance cost, it isn't economically practical to expect it to hit critical mass and the everyone stops writing v4 specific code and config. IPv42 or whatever will be a good solution will be economically viable requiring the smallest change by end users and producers. V6 was developed by a committee of network engineers that only saw things from a network operator and vendor perspective. The lesson from sunken cost fallacy is that existing investment cannot be used to justify continued investment and in this case the problem of v4 shortage has been addressed by other means in a way that will keep it alive for decades more.

In my opinion, a solutiom that requires a firmware update that can work with existing ASIC and is economically viable is possible but the discussion about that isn't even happening. Billions will be wasted on the hopes that decades from now ipv6 can stand on its own.