I relate extremely to Arthur Fleck (or the joker) and was glad when it ended the way it did. I'm very glad and happy, because I'm going through a rough time dealing with loss, and the way Arthur lost Harley, and that there was no happy ending, it made me feel sympathetic for his loss and life. Arthur used to be my idol, because of how relatable he was. Seeing in the beginning him being in jail like I was when I was incarcerated, and how skinny he was, he looked exactly like he felt: empty and detached from others, Even his own environment. I loved how he danced and sang even when at the lowest points, and was smiling no matter what. When he was not joker, but said it was really all a fantasy, I could sympathize with him through it all. Loved it, perfect movie and thank you for it. It's helped me feel better, and about my loss.
And also, I loved seeing joker singing and dancing on stage like we were at a ballroom, because there was no theatres back then, so what do you expect?