I totally get what you are saying, and I have ver mixed feelings about real life serial killers films. However, I must say I loved this film.

I don't think there is a moral to the story. He doesn't win... he goes to the nut jail and in the end will find batman. And I don't think he becomes the hero of the city. More like the destroyer of the city and the leader of a very sick group of individuals.

The humour... well I did laugh at some points. But the film is completely a greek tragedy/ opera about a "sad" and crazy antagonist.

I think it was a movie not about the joker in action but an intimate look into the "creation" of one of the biggest criminals of the city ever. And it does not leave society itself out of the equation, while not making it sole responsible.

Since it is a completely fictional antagonist that we know very well... it gave the permission to go some interesting places. A nihilist movie about a very sick man. Anyhow, I really liked it and I "got/agree" with some things you said, so I wrote my 2 cents here.

Have a nice week.