Sure there is a sense in which Navajo is really hard to learn, but that's the same sense in which it's very hard to learn Babylonian/Akkadian. It's hard because

Sure there is a sense in which Navajo is really hard to learn, but that's the same sense in which it's very hard to learn Babylonian/Akkadian. It's hard because no one speaks it, there is no culture to immerse yourself in, no theater or movies you can watch, no music you can listen to, no novels you can read, no friends to speak with, etc etc... The only way to learn Akkadian, or Navajo, is in a very artificial and academic manner, and learning things in that fashion tends to be very inefficient.