The second Joker movie had a lot to live up to. There was always an underlying tension, which was expected to erupt into chaos and violence at any time. But sadly that moment never came. What was left was the sad story of a mentally ill criminal going through his trial and gaining some hope when falling in love.
Beware: spoilers ahead
Although despised by most of Gotham's citizens, the Joker had a loyal fan-base. Then, later in the movie it gets clearer that those fans were only interested in the monster-part of the joker, but not in his person. When they realized they weren't given the monster, their support and loyalty faded quickly, leaving the Joker alone and devastated.
I think the main idea behind the movie is interesting and engaging, but the execution is way too lengthy. It lacks an action part where the Joker and Harley Quinn drown the city in chaos. The singing scenes were too numerous and his mentally illness may have been expressed better while wrecking the city.
The acting, the art style and presentation were awesome, that's why the short story in such a long movie disappoints even more.