Gods and Monsters is an interesting premise. The trope of an alternate-reality Justice League that have gone full-totalitarian state on humanity is a commonly explored one, but I don't think I've ever seen it where the story doesn't become about them trying to enact their form of justice on other realms. Instead, we get a backwards origin story, where the heroes already exist but act like villains and the villains are more fail-safes on the heroes. By the end, the two groups come together for the general betterment of mankind. I'm not really too sure what the moral is meant to be, but it's an interesting Elseworld's style experiment.
Unfortunately, those riffs on the more common hero setup are the big appeal here. The actual plot – about a disgruntled scientist attempting to remake the world in his image – is fairly dull. The intrigue comes from seeing characters we know so well in a new light, with people like Lex Luthor basically playing the role of Marvel's Watcher or Amanda Waller genuinely having humanity's best interests at heart, for example. Plot progression is largely driven by happenchance and liberal usage of killer robots with boom-tube tech, so it never really feels genuine. Nor do I ever really care about the actual villain.
It boils down to a well-animated thought experiment that I feel would have been better as a series of shorter, one-shot style snapshots than a feature film.