The Yoke of God.
For good or ill, the personality of every non-native American of the late 19th or early 20th century was a reaction to God, grounded in the choice to accept or reject the fight between god & the devil for your soul. The Western as a genre fit the Hays Code perfectly on that basis - that a fella or a gal made that choice & paid that price. Zero sum.
The characters in Hateful 8 simply don't work because none of them have made that choice - they are all modern characters, unburdened by salvation or perdition. And, by the actions of his characters and motive of his stories, the writer/director makes it clear he is not transposing modern characters intentionally to see the affect of the milieu upon them. He just missed the essential element of the reactive patterns of every one of his characters, rendering his tale an immature, unsalvageable effort from the start.