I had interest in seeing it, because the left-of-center places where slamming it, and a few right of center ones were pointing it's merit.
Without too many spoilers, the "Clown" that will be Joker is becoming a bit infamous as an anti-hero in the city, because of an altercation with rich assholes, and the crumbling corrupt city has the "eat the rich" attitude of Bernie Sander / Elizabeth Warren, while the guy running for Mayor is a douchebag Hillary type elitist treating them like unwashed deplorable's and "clowns". Since this death spiral of progressivism is likely to lead to a deep/dark place, I think it hit a little too close to home for some of the lefty movie reviewers. But the audience's higher ratings for it, seemed to get that it wasn't really overt political commentary on any one side -- it was just about angst, frustration, and any dark dystopia. So it's sort of a Rorschach Inkblot, in that you can read in the motives you want... but some didn't like what they saw. (Which is good, it might hint that they do have a microgram of introspection in all their finger-pointing zeal).
It was deep, dark, cerebral, well acted, well directed, the story told a message (but was slow, low action, and all in the mind of a suffering individual)... but it was like One Flew Over the Cuckoo's Nest for the New Millennium, and sans humor. So if you go into it, knowing that's what you want to see, then