Phoenix's performance is the only significant point of praise for me, elevating the film above just middling. It's too bad such a great performance was largely squandered on bland material.
Killing Joke's (possible) origin for Joker was so much more interesting, taking a humdrum little man and unleashing a series of tragedies upon him in a short span of time. This film makes Fleck a constant source of abuse from virtually all aspects of society, even giving him a handicapped mental state to begin with.
De Niro continues to phone it in, even in what everybody knew would be a big movie. It's difficult to distinguish between his performances in cinema and something like Saturday Night Live, which is just so sad a thing considering he's given cinema some of its all-time best performances.
Spoiler!
The Sophie twist was predictable. When I saw the first trailer, I assumed she would be revealed as imaginary, which was damn close to the film's revelation.
Having Thomas Wayne possibly be Arthur's father is just silly, as well as pushing a meeting between Arthur and a young Bruce Wayne.
Will people be as annoyed about Joker (this time, inadvertently) getting the Waynes killed in this as they were about Napier murdering them in Burton's film? It was so unnecessary, and a ridiculously forced tie-in to the larger Batman mythos.
I keep reading praise from people who claim that this is some kind of 'deep psychological study of a disturbed man' or some such. But it's really not. Joker is one of the most evil and enigmatic fictional characters. What this film does is give him an extremely boring backstory:
Poor man is victimized by society until he decides to fight back, only he takes it too far. That sounds like the delusions of most spree killers, which are really not that interesting at all.
Hopefully Phoenix maintains recognition for seemingly giving his all when most simply cash in on brand name properties. But I have a hard time imagining people dissecting this movie for years to come as they would if it were as good as the hype.