It's a fair question.
While Joker is a DC comic character, he's merely the vehicle for what the movie is really about.
You could've dropped in a regular Joe and called the movie "Joe" and it would've been the same.
It's a movie about severe mental illness and what can happen when someone is on that downward spiral.
The overall tone of it is something I didn't need or want to feel. I'm not saying it's a bad movie, or it's not well done, just for me I wish I wouldn't have watched it.