Disappointing to say the least.
As an action film, it was okay. If you were expecting to learn anything about the Navajo Code Talkers other than the fact they existed during WWII, then expect to be disappointed. It was little more than a war movie with fictional characters with a bit of code talking thrown in to drive the plot.
A good film to make about code talkers would be one based upon the book Navajo Weapon by Sally McClain. Excellent book from start to finish. It details how the code talkers were first created and how they helped fight the war. https://www.goodreads.com/book/show/816141.Navajo_Weapon