I absolutely agree that it is a bad bad bad idea to have admin endpoints for your routers visible to the public internet, and that anyone with real responsibility for networks or infrastructure of any kind needs to know that. Moreover, no matter how much improvement there is in software quality, that will probably remain good advice--why not add an extra layer of protection?
On the other hand, it makes me sad as an industry that it's certain doom if you don't follow that kind of advice. Why don't we have simple web servers that offer secure admin interfaces that can be plugged in for various products? It's not as if the user interface for a router's configuration is bleeding edge technology.