To me this may be a crime/drama from the 80's and they just decided at the last minute to use the joker as the main character.
From Kotaku
"If
Joker wasn’t called “Joker,” you’d never know it was a DC movie. Though there are characters with the last name “Wayne” and it takes place in a city called “Gotham,” there’s little else that distinguishes Todd Phillips’ latest film as a comic book movie. It’s a solid, well-made film that, ultimately, has a bit of an identity crisis.
Joker isn’t quite sure what it wants to be. What it definitely
is is a movie about a disturbed man named Arthur Fleck,
played by Joaquin Phoenix. Arthur is a clown-for-hire who lives with his mother Penny (
American Horror Story’sFrances Conroy) in a powder keg of a city that’s just waiting to explode. And, without really even realizing the impact his actions are having on the outside world,Arthur ends up lighting the fuse.
Joker is a comic book origin story with very little comic book in it. The whole thing very purposefully feels like a love letter to cinema of the late ‘70s, early ‘80s rather than other dark DC superhero movies like Tim Burton’s
Batman or Christopher Nolan’s
The Dark Knight. Using that gritty aesthetic, Phillips is much more interested in dissecting what makes a comic book character real than making a real comic book character and, in that aim, he’s successful. Arthur is a fascinating and endlessly compelling person. He’s also terrifying and, for most of the film, sympathetic."
Would explain why it is so good then lol.