The film provides great insights into Indigenous culture, a good story, and a wonderful new monster!
The Moogai itself is a bogeyman with a very effective nightmarish quality. It seems to me to be a metaphor for a new memory of white government stealers of children. It is pale skinned and two-faced and wants to take children for mysterious reasons of its own: just like the actual government officials did. The name Moogai is very similar to the word for white people, Dogai. No doubt a few generations ago the parents of Indigenous children would have told them to run from the Moogai/Dogai to avoid being taken.
So the real history merges with the ancient myths.
There is a clever interplay of themes regarding mental illness, bigoted attitudes, traditional myth and past attitudes of government officials. A lot was covered.
The climax was horrifying mainly to the brilliant monster which will give you nightmares.
