Put simply, the revisionist Western steers away from, or plays against, formula, refusing to romanticize the Old West or depict it as a place with clear good guys and bad guys. It also tends to emphasize the grimier, more unpleasant aspects of life in the American West. One litmus test: If you see flies buzzing around a corpse, you’re probably watching a revisionist Western.
https://www.vulture.com/article/50-best-western-movies-ever.html