Idk why ppl say it's bad. I loved it! Every second was beautiful in the same way an inevitable tragedy is - when you can't turn away.
Spoilers:
I loved the feeling of not being able to decide if I wanted more Joker - he was glorious; or Arthur - he was pitiful but also, relatable in his hopes and vulnerability to the point where it was painful. The court scene with Puddles was amazing. The way Lee's actions tied in with the ending - and a new Joker made me wish desperately for a third movie.
The only thing I wish they did better was the scene with the guards taking revenge on Arthur. I wish it had more brutality, to shock the audience and to drive the point home with gruesome violence to contrast the metaphors. It should have been bolder and uglier. Like a bucket of ice cold water.
Other than that, impeccable movie. 11/10.