The joker is the worst one to use here regardless of the universe you use. In that particular universe he's more akin to the weird fucking red pill/mra movement than an anti capitalist since he was loosely based on Bernie geatz. It's why the maga sphere went crazy for what was a series of terrible movies that they entirely miss the point of.
I think the message is that there's a thin line between the hero and the villain. The villain feels the same anger and desire for justice we all do. Just add a bit of delusion, and you can turn Gandhi into Hitler, or Batman into the Joker.
It's really not though, it's about modern moral failings and their outcomes that happen to have economic effects and notably none of the issues persued in the movie are exclusive to capitalist models.
The Batman universe is to some degree anti capitalist but the protagonist being one of the richest people in the planet who cannonically got that money by theft, violence and arms dealing kinda cancels that out.
You can read what you want into it but it specifically was not anti capitalist. It's outright glorification of the Bernie geatz model, ie. A crybaby lower middle class white man who goes bat shit on the subway and blames literally everyone else but himself.
Similarly Bernie geatz was very much a capitalist.
Friend, I'm not gonna slam you because it's clear your intentions are right, but you are misunderstanding the movie big time. I want you to watch it again and pay extra attention to the subway scene and who those people in the scene were.
I think you're misunderstanding the movie friend and none of this was intended as a "slam" so I'm not sure why you would bring that up anyway.
I have no intention of rewatching either of those dumpster fires. I do love it that the right sees the Bernie goetz vigilante shit and goes "oh shit that's the point! We gotta take these probably into our own hands!" And you get white nationalist mass shooters that reference the joker. The left goes "Oh shit this movie delves into the moral failings of a deeply sick modern society and also how money is evil... It must be anti capitalist!" It's just not, it's a case study on the moral failings of society through the eyes of the mentally ill, the fact you see it as anti capitalist is your mental illness and that's the point of the movie.