NAT is not only bad because you don't have publicly routable addresses, but because it's a hack and a pretty "clever" one at that, aka, incredibly nasty. If we

NAT is not only bad because you don't have publicly routable addresses, but because it's a hack and a pretty "clever" one at that, aka, incredibly nasty. If we had networking protocols that took into account the complexities of private addresses it could probably work - but we don't have such a luxury. The entire TCP/IP stack assumes peer to peer connections, and NAT is literally a spanner in the works for all that.