It's true that the movie doesn't come out and tell you exactly what the point is or what the lessons are, which makes it very unusual for a Hollywood film. But the point IS there, it just takes some thought. If nothing else, it's a movie about how change is scary and how much anger hurts a family.
One example: at the beginning of the film, Max expresses rage and resentment at his sister and mother leaving him behind to spend time with new people he doesn't like or understand. This is later mirrored by Carol's rage and resentment over KW's new friends. At first, Carol and Max bond over these shared negative feelings. But later, Max comes to empathize with KW's position and see that Bob and Terry are harmless, if incomprehensible. He invites them to join the rest of the group and even stands up for their right to be there when Carol gets mad. That's a big change of heart right there.
A possible YMMV example; both of the times Max is shown losing control in the beginning, he ends up feeling sad, hurt, and regretful afterward. You could even say the reason he runs away is because he was frightened of how he got so mad, he bit his mother. At the end of the film, in the wake of Carol's furious rampage, Max leaves behind a heart to show Carol that he even though he got mad and it was scary, Max still loves him. Then Max makes it home and even though he'd gotten mad and it was scary, his mother still loves him.
The mother loved him so much she didn't even bother chasing after him?
She chased after him; she just eventually lost him in the forest at some point and thought it wiser to go home and get help or something.