Remember this is a kids movie
After many, many, many animated Productions whith the intention to attract adults, many people forget that not all kids movies have to be like this.
This movie has more modest intentions, entertain new generations of children, and bring nostalgic to adults who enjoy this show. Another point to keep in Mind is the fact the movie is mexican and the humor sometimes isn't the same for anglos than for latinos, I supose the dubbing actors in english do their best, but is hard. Same thing with some american comedies in Latinamerica.
About the complaints of the quality of the animation, a Latin American film can hardly have technology budgets of the big american studios like Pixar. just a recent movie called 'metegol' about table soccer dolls are starting to compete a bit with that kind of look.