The Navajo language isn’t being passed down the generations. It was so unknown, hence the code talkers (other NA languages, too) back in WWI. Can’t see how many NA millennials would understand movies without closed captions. But, hey, diversity is soooo waaaay coooool!
I’m Navajo. I see some kids successfully learning it. Mostly in the core of the reservation. Sure it’s a bit tough but doable. I can speak it ok. I can understand it fluently. There’s even a King James Version bible in Navajo. I can read that good. When I was growing up, we had 2 white traders who ran a trading post in our store who spoke it fluently.