Joker is hated by mainstream reviewers for showing unapologetically, albeit in dramatized style, the harsh reality of systematic abuse and apathy the mentally ill and impoverished face every day. It takes the radical position of depicting people similar to the fictional Thomas Wayne as not the solution, but rather the problem. The poor to people like Thomas Wayne are clowns, not even worthy of contempt. If only they'd work as hard as he, then maybe they'd share his wealth and success! Or so he'd like to believe. His son Bruce will presumably grow up to become Batman, a rich spoiled vigilante that gets his kicks by beating up opportunistic criminals in an urban environment of decay and destitution. Like his father, Bruce is merely part of the problem at best is a symptom of a society facing total moral collapse.
Arthur from the moment of conception is abandoned and left to be abused by a narcissistic "caretaker" and her bad boy boyfriend. He grows up horrifically broken and fantasizes receiving fatherly love from a talk show host. This is the kind of man that is starved of love and has known only the vicious callousness of his anomic society.
It's hard to say if Arthur would have grown or developed normally to begin with, but the fact of the matter is: he is given no chance or hope. His only path is to become insane. All other doors have been shut...
Instead of helping Arthur, his society cuts his meager therapy and leaves him without his many prescriptions. Arthur is subject to physical abuse without any recourse. And the man he came to fantasize as a fatherly figure, ridicules and mocks Arthur for the sake of empty entertainment. The end result is not surprising.
Amazing cinematography and Joaquin Phoenix proves again he's one of the best in the business. The Joker proves that you don't need fancy special effects and a myriad of explosions to make a good and profitable superhero movie.