Down at it's deepest level.
This film is about Fathers and Sons. A Son's wish to reach back through the years and help his Father, and a Father's unending desire to guide his son to be the most he can be.
Wish fulfillment, sure. But getting older now, seeing this story from both sides, it's hard for me not to identify with what drives both the leads in this film, regardless if the story get's a bit "out there" in its ultimately "best case" ending.