> 464xlat allows communication from ipv6 only clients to legacy ipv4 ones without the need for a separate stack on your end device
> nat46 allows communication from a legacy v4 device to a modern v6 device without the need for a separate stack on your end device
How does that work if your ISP doesn't support IPv6? Can an OS developer deliver IPv6-only OSs to any end user? How about v4-only VPNs? Ultimately the answer is that devices must support both IPv4 and v6 until the day only one remains. Keeping both active at the same time may be more optional, but there is plenty of software which assumes IPv4 at other layers than simple connectivity. So running IPv6-only is generally a bad idea even today.
This whole discussion was about what should have been done differently at the start of the IPv6 rollout to help it complete in less than a lifetime, not about the situation some decades in.
But that's what I mean: lots of ISPs have supported IPv6 for 1-2 decades. Most hardware & software already supported it a decade ago, and nobody should be using anything that old without updates. The only reason for an ISP today to not provide it is incompetence.
Two decades ago I was a member of a ISP consumer group, and we discussed it with a couple ISPs back then. They all were working on a planning for it (one smaller ISP even already implemented it back then!). Apparently in other countries ISPs were allowed to behave irresponsibly.
Really, the only way to force such incompetent ISPs out is if governments get involved, or if all/most backbone providers and IX operators set a date where IPv4 will become very expensive, and then one where it will be switched off...
> nat46 allows communication from a legacy v4 device to a modern v6 device without the need for a separate stack on your end device
How does that work if your ISP doesn't support IPv6? Can an OS developer deliver IPv6-only OSs to any end user? How about v4-only VPNs? Ultimately the answer is that devices must support both IPv4 and v6 until the day only one remains. Keeping both active at the same time may be more optional, but there is plenty of software which assumes IPv4 at other layers than simple connectivity. So running IPv6-only is generally a bad idea even today.