Oh by the way, Todd Phillips confirmed the sequel is indeed pointless and it only exists because we, the viewers, are a bunch morons who expected Phoenix to fight Batman. Or at least that's how Todd interpreted the discussion people were having.
"Todd Phillips: One of the things that people never understood about the first movie was, “I don't get it. He visits Bruce Wayne and he's 30 years older than Bruce Wayne. What kind of geriatric Joker is going to fight in the future?” I don't know if you've ever saw the script of the first movie. The first film is called Joker. It's not called The Joker, it's called Joker. And the first film under the script always said "An origin story." Never said THE origin story. It was this idea that maybe this isn't THE Joker. Maybe this is the inspiration for the Joker. So, in essence at the end of this movie (Folie à Deux), the thing you're being left with is “Wait, what is that thing happening behind him? Is that the guy?”
The main reason the sequel exists, is to show Arthur was only the inspiration for the real Joker, as that is what was planned from the beginning.
I don't know about you fellas but that flew right over my simpleton brain, perhaps the first movie should've just ended with Arthur getting shanked by Temu Ledger, that way there'd be no doubt left in my mind that middle aged incarcerated Arthur in a timeline with child Bruce, would not be facing off Batman in his life time.
But I guess I just had to watch a 2 hour musical of the character being destroyed, demoralized, raped and murdered to realize that.
Bravo Phillips, thanks for enlightening my feeble brain with your thought provoking piece of cinematic art!