Just meh. Certainly one of the movies of all time.
Giant spaceships, ominous shadows, a young hero, a grizzled warrior. Trademarks of a Snyder film. But, feels empty and the story segments feel disjointed. The characters are not believable.
Star Wars, Harry Potter (Hippogriff), Doctor Who (Spider which is also a grieving mother), Seven Samurai, Wild Wild West and Spaghetti Westerns. Put those in a blender, take out character development/emotions and you get Rebel Moon. Interesting idea, horrific execution.
One time watch for the hype.