Since 1980 we have believed that universal connectivity was one of the great achievements of the Internet design. Today, one must unfortunately question whether universal connectivity can be sustained (or is even the right goal) in a networking environment without universal trust.
I think we can safely say that 99.99% of all systems that run IP don't want to talk to 99.99% of all systems that run IP. For most people, with a network this large, universal connectivity isn't a goal but a threat. But this shouldn't be confused with universal addressability being undesirable, because this only gets more important as the size of the network increases.
Maybe NATs are, in fact, a result of a very deep problem with our architecture.
Yes, that IP addresses are only 32 bits. So people decided to usurp the 16 bit port number to create virtual 48 bit IP addresses.
If you accept that, then there is no point in attacking NATs until you can propose a better architectural solution to the trust problem (hopefully, there will be one!)
What we need is a good way to limit access to systems. Firewalls look at addresses and port numbers, which are mostly meaningless. So people hide their boxes behind NATs and bastion hosts to gain some security. If we can solve this IPv6 will take care of the rest.