I think something I always enjoy in serious movies is when it shows brutal honesty (which this movie did show) because for Arthur AKA The Joker even though it seems harsh and cruel the world might not have anything nice to say about you and also chooses to abuse and mistreat you, even if you are a nice guy struggling to remain sane amidst your mental and psychological demons that you try your utmost to suppress but the world seems hell-bent on you giving in and succumbing to those demons.
They might rue the day they chose to kick a man when he's down and may have thought "he's probably just a loser outcast anyway"
This world may force you to choose an identity a sort of Yin and Yang if you will
You either choose to shoulder the burden and accept the way things are, always suppressing the Injustice and the cruelty of the world, or you give in to that dark side and always live completely unhinged, never bridling any of your desires no matter how frivolous or despicable they turn out to be.
Possibly the quote "You either die a hero or you live long enough to see yourself become the villain" could very well be the underlying idea of this movie.
One thing I'll say is you never seem to know what the Joker is thinking at least in my opinion I guess you could say his Insanity is uniquely his own and he's the only one who can truly understand it.
Interestingly this movie may leave you feeling somewhat sympathetic for him at least I felt that way. The thing that seems stuck in my head and I can't stop thinking about it is, society may in fact breed the Psychopathic Killers when it tries to claim that it's striving for a utopic vision.
I feel quite stumped, it's hard to put a label on the Joker is he a psychopath or a sociopath maybe someone far more knowledgeable on those two things could figure it out LOL.
In the end I'd recommend it, I'd say it's a surreal, visceral, experience and for that much I think it's worth watching.