Canyon de Chelly is a National Monument, but it's located entirely on Navajo tribal land. Although it's federally protected as a National Monument, it's a tribal territory.
You missed an incredible experience by passing up the tribal jeep tour. In my opinion, this should be a required experience for all Americans. Having a local Navajo guide professionally lead you through the canyon is an invaluable history lesson.
My parents took our family there when I was young and I took my family there once my kids were old enough to appreciate and understand it.
When I was in fourth grade, my teacher (an otherwise great teacher) was lazily reading out of our history text about the great American hero, Kit Carson. I literally jumped out of my seat and told her that none of this was true and asked her if she knew what he did to the Navajo people. She told me to catch my breath and come up front and tell the class what I knew. I repeated what I had learned about
The Long Walk. The teacher thanked me for my alternative explanation and used this as a chance to talk to our class about perspective and bias in historical accounts (including my own obvious perspective & bias).
It's a beautiful area with rich history. I wouldn't trust the NPS to post signs to accurately depict the stories. The local guides do this better than any signs could.