Given how popular Batman is and how long the character has been around, not doubt it’s difficult to come up with original story ideas for him, but in the case of this movie, putting Batman into another fairly popular fictional universe, the Cthulhu mythos, worked out pretty well.
It had a nice blend of both Batman and Lovecraftian lore. On the Bat’s side, given that the story is set in the early 1900s, the tech isn’t the same as in stories in more modern settings, but several familiar characters appear in this movie, though done up a bit differently. From Cthuhy’s side, there are ravenous mutated penguins and cults and sinister tomes and great madness-causing beings with strange names.
I fairly well enjoyed it, overall.