This movie is one of the most genuine feeling portrayals of a person who has had a rough and lonely life.
All of the acting is first-rate. Mahershala Ali deserves his "Best Supporting" for a nuanced, strong performance in a role that's essential to setting the groundwork for this story, and also, let's face it, for sheer charisma, but every one else was also terrific, including Little at all his ages, Kevin at all his ages, Janelle Monae, and the heartbreaking Naomie Harris.
This is a humanizing movie; if you have a heart at all, seeing it makes you want to give people a break when you wonder why they do the crazy or criminal things they do. That said, I'd love to see a cast this strong do a modern story mostly removed from the 'hood. The setting enhances understanding but probably also reinforces stereotypes.