Don't see why this movie is getting so much hate. I loved it. Yeah, some of the musical bits may be cringe, but that's because people are not used to seeing "Joker" doing such things. We were told that there are musical parts before it's release. Also, I can point out that Grease is a musical, Sweeny Tod is a musical, Nightmare Before Christmas is a musical, Hocus Pokus is a musical, and man, I could go on forever! 🤣 You dont see many people hating those movies... And besides, the musical bits mostly happen in Authur's mind. Like daydreaming...
The ending kinda makes sense to me. So don't read this bit if you haven't seen it yet.
Authur or "Joker" gets shanked to death by an insane inmate. He's a younger guy that most likely been influenced by Authur's actions. He tells Authur a joke, then stabs him several times in the stomach. Authur falls dead to the floor while the inmate, takes his knife and cuts his own face with it. Seems like he cuts a smile into his cheeks. Can't tell too much, because the camera mostly focuses on Authur twitching and dying. Now since the inmate is young and crazy as hell, I can see that the real "Joker" has been revealed. It makes sense to me, because around this time, Bruce Wayne is probably the same age. We seen him as a kid in the first movie. So, by the time this new "Joker" gets out of Arkham, Batman will have his archenemy to deal with.
So the way I comprehend it is, the Joker movies are prequels to the later Batman stories. They create the persona of the "Joker" by the actions of Authur. The young inmate gets heavily influenced by him to become the actual "Joker" that we see later on.
It'll be cool if we get a third film, but I don't see that happening. Maybe the creator will make a Batman film based off of the Joker films years from now. After this new Joker movie becomes a cult classic or whatever. When something new like this comes out, there's a lot of hate for it because it's different. Then years later, it's beloved by many.