"Ivory tower bullshit that is completely out of touch with reality."
So what are they going to do instead?
Option 1: Vendors will design routers with a big off-switch on the firewall so that every device on the LAN side is directly addressable. Result: said vendors' customers are totally raped and burned within minutes of switching the device on and the vendors, along with any ISP daft enough to foist such crud on Joe User faces lawsuits for apocalyptic levels of negligence.
Option 2: Vendors implement UPnP for IPv6, or its moral equivalent. A daft idea, but no less secure than implementing it for IPv4. In both cases, a device (or malware running on the device) on the LAN side is able to bypass whatever firewalling restrictions are in place without the user's knowledge. In neither case, can an external host force its way in without help from the LAN side.
Option 3: What I said.