There's a big difference between routable (on the Internet) addresses and non-routable addresses. For one, you can trivially merge two different sets of resources (say from two different organizations or projects) without address conflicts, if they both have globally unique, routable addresses.
LAN networking is great. Internet networking is so much better, it has effectively given birth to a new technological age.
It absolutely is a showstopper if you don't have applications that are NAT friendly. And in 2016 if you are forcing people to use NAT and claiming that's a fix, you're doing the entire world a disservice.
I've been hearing this argument for 15 years now and it hasn't changed. Sure, there's a public address shortage these days, but the incessant whining by end-to-end purists who think NAT is an unbearable sin falls on deaf ears just as much now as it ever did.
I'm not against V6 by any means, but internal IPv4 private subnets are simply not a problem for the 99+% of who still somehow manage to get things done in the real world.
LAN networking is great. Internet networking is so much better, it has effectively given birth to a new technological age.