I think that’s intended as a feature. IPv4 is just not good enough, we will run out of addresses. I think they want to kill IPv4 and replace it rather than improving upon it. At some point programs will ignore IPv4 altogether and our IP addresses will not be fundamentally flawed anymore.

layers are only ever added, never removed

So far no one ever managed to come up with a plan that is backward compatible and does enough. (Aka the fundamental problem is that if you change v4 semantics you have to deploy new software/firmware/hardware, and if you are doing that anyway, a clean slate seemed like the easier option.) And don't forget v6 has well defined semantics with regards to v4 interoperability for a lot of things (::ffff:, NAT64, DNS64), so you can be on v6 and reach all of v4 via a gateway.)

that's not true. you can have IPv6 only in the backend and expose IPv4 only at the very frontend (like Cloudfare does the other way around).

Dual stack are not really needed and usually add complexity for few little benefits.

The main problem of IPv6 is the lack of people willing to learn it, teach it and adopt it.

Something brand new like Kubernetes should have from the start been IPv6 only , with IPv4 at the egress parts only.