I don't think there has be a point to a movie, but I can agree with you that compared to Joker, there is not the same level of commentary on society.
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Lee, the press and most, if not everyone in courtroom, had no interest in Fleck at all. You could almost say that no one cared until he put the mask on. They were there for the freak show.
Despite being off his meds, he eventually realizes that he has become a monster and the moment he decides that he does not want to be the Joker, he stops singing while Lee continues. (Meaning he is out of his delusion, but she still gaga).
I thought that way he was killed off in the end was brilliant and it fits really well with the whole Joker myth. A Joker also (probably) died in Gotham (the show - Admittedly kind of shit) while explaining how he is an idea that can't be killed. Sort of explains the vagueness of his origin(s).
Hell, this even opens up the possibility that Joker is in fact an immortal, skinwalking trickster demon. I would like that very much.
This storyline sadly won't go any further probably, but it leaves room for a new Joker being committed to Arkham, meeting Lee who now works there (she's a psychologist after all) and yadda yadda yadda, the "original" Harley origin could take place. There has been storylines in comics about Harley's pregnancy as well.
Fuck ja!