v4 doesn't even manage one IP per person. It's fundamentally completely insufficient in a world with personal computing devices. Even if you declared every single IP in v4 to be wasted and demanded we repurposed them all, it wouldn't be enough to fix that.

The multicast and reserved blocks total 32 /8s. Before IANA runout, we were going through over one /8 per month, so this would represent less than 2.5 years of allocations. We've already spent decades buying more time for people to migrate to v6; we don't need another 2.5 years that people will just immediately squander.

NAT is not in any way a feature. I'll admit it can be a useful tool in your toolbox sometimes, but otherwise it's just a completely unnecessary complication that breaks things and wastes time and effort. It's not something to be building the Internet on. You want each device to get an IP and you don't want two devices to have the same IP, because that's how machines on the Internet send packets to each other -- which is the entire point of having the Internet at all.

> All of "the global internet" is in 2002::/16, which effectively gives 32 bits of assignable space. Exactly the same as IPv4 [...] the assumption that all routable prefixes are in 2001::/16 as specified

Global allocations are actually coming from the entire of 2000::/3, not 2002::/16 or 2001::/16 (and there's another five untouched /3s in case we need them). So far about 0.2% of it been allocated to RIRs, and most of that RIR space has not yet been allocated to anybody. We're clearly not exhausting it at anything like the rate of v4.

v6 is less complex than v4 in practice due to not needing NAT, and gains us far more than you're thinking. A /48 contains 65k subnets of effectively infinite hosts each, which is similar to a /8 but with no limit on hosts per network, and there are something on the order of a trillion of them in total rather than 256 of them.

Sure there is: use single-stack v6 with NAT64.

What you're describing there is just an approach to store NAT state inside every packet instead of on the router. I'm not sure that's even an improvement on v4, but in any case it wouldn't increase the size of the address space so it wouldn't help with the one thing driving the need for IPv6.

Two 6to4 networks will communicate directly between each other without using a relay, so it will still work for that. Although you ought to be able to use native v6 these days.

If you can't deploy v6 (whether native or 6to4) on the remote side for whatever reason, NAT64 is useful for dealing with conflicting RFC1918. You map each instance of RFC1918 you need to access into different v6 /96s, and then they don't conflict from your perspective. (But like NAT44, it only works for outbound connections; inbound ones need a port forward.)

If your DNS server isn't replying to requests, your DNS server is broken. That has nothing to do with v6.

Plenty of people are switching v4 off. Facebook run basically all of their datacenters without v4. T-Mobile USA use only v6 on their network. Thread only supports v6 in the first place

There are plenty of other places doing the same thing, but these examples alone should be sufficient to disprove "no-one is willing to turn v4 off".