Sorry, this movie looks lame. It isn't tied to the overall universe, its just a character study that will have no ties to anything larger. So that makes the performace even that much more frustrating, because it will go nowhere, this is a one-off movie. The real DC cannon will cast Will Smith's son as the next joker in the main series, so why bother.
Just name this movie something else and keep all the touch points the same. It's core foundation is the comic series, which the actor pulled off well, but its not going anywhere so why bother.
I don't get it. Just make an art house movie about a troubled mentally ill dude.