This movie makes so much logical sense to the true character and identify of Joker โ that NOT being Arthur Fleck. As an audience member, symbolized by Harley Quinn, I wanted Arthur to have a character arc to become the Heath Ledger - style joker we all know. However, we are left with disappointment when that doesnโt happen, just like Harley is โ which was done by design. Arthur was a depressed and broken man, who accidentally created the Joker movement. However, he never had the personality to truly become the genius supervillain of Joker.
The disappointment is part of the movie experience. Joaquin Phoenix did an incredible job portraying joker, his mannerisms and movements. His overall look in those truly Joker-esque scenes (e.g. the slowmo subway scene with the cigarette in the first film), made me truly believe he could be THE Joker. However, looking deeper at Arthurโs characterโฆ it just makes more sense that he wasnโt fit to be that supervillain. It makes much more sense that Arthur accidentally created the movement, and a true psychopath would be the one whoโd take over as The Joker in the end.