Ain't even close to the rating it has.

Rating: 6/10 (15 November 2019)

I'm going to just briefly touch on three things: The movie, how it relates to DC and how its IMDB score has nothing to do with the quality of the movie.
The movie was somewhat entertaining. It took a little too long building up his personality. Frankly it got boring during the first half. There's nothing that I would say is "dangerous". Anyone stupid enough to use this film as their motivation for some criminal act has no one to blame but themselves. Joaquin Phoenix is possibly one of the best and versatile actors still currently in his prime. His skills are the highlight of this entire movie and I honestly think without him, nothing would work here.
I think its pointless how this is even associated with DC comics. It could've been just as good if it were not tied to the comic. Actually it would've been better because I have no interest in a deep character study drama being tied with Batman. If this movie does continue on (which you know its gonna be milked dry) all of the timelines and ages are all screwed up. I always liked not really knowing The Joker's backstory. I also hated the idea that society created the Joker; like all of us should feel partially responsible. Much better movie if you get rid of its ties to the DC cinematic universe.
Lastly, the score this has (currently 8.8/10) is 100% fabrication and backlash from the Rotten Tomatoes scoring. Back when this first came out, the fans gave it a high rating while the critics went super low. I believe that the IMDB rating for The Joker is fake. I mean come on, 8.8?! This puts it in the top 10 just behind 12 Angry Men and beats out classics like Lord of the Rings, Fight Club, Empire Strikes Back and Terminator 2......please, there's no way this movie is even close to being that good.
Bottom line: Its an ok movie with some slow burn (sometimes too slow) and its link to the source material holds it back because it doesn't need it to be as good as it is. Mediocre at best.