Ok-- I am no comic-book aficionado, but I do recall reading Batman/Joker comic books and being profoundly disturbed by them. The portrayal of the Joker in the comic books is that of a completely amoral, perverse, disturbed, evil, psychopath and murderer of hundreds (thousands)? I don't believe that this character can, or should, be translated to film. Tolerable in 2D; his hyperbole, will either come off as too grotesque or it will be over-the-top and campy/ridiculous. I don't think a movie audience is ready for a true depiction of the evil that is comic book Joker.
(Also, I can never understand how Batman could sleep at all knowing he always lets Joker live and then he continues to kill scores of people).
I guess Batman wouldn't do well with the go-back-in-time and kill baby Hitler scenario either (nod to Deadpool 2).