Many great movies are meticulous, laser-focused affairs, films that have a mission statement that they zero in on early and hew to from the first frame to the last, using every facet of the script, visuals and performances to reinforce this single imparted truth. This can be especially helpful with family films meant for a wide child audience, allowing a movie to be accessible and stimulating to a young audience in a "digestible" manner.
And when properly executed, it works like gangbusters. The environmentalism of Miyazaki, the self-actualization of Brad Bird, the praises of true love through acceptance in Frozen or Beauty & the Beast, or the message of friendship until the end of the Toy Story films - the results speak for themselves.
But rules are made to be broken. The Book of Life takes a different approach. And while the result isn't the sort of richly-crafted masterpiece of message, tone, and perfect plotting seen in these previously-mentioned cinematic titans, it creates a beautifully unwieldy magic all its own.