Finally saw the movie tonight. I thought it was cute and fun. A lot of laughs and a TON of in-jokes and references for the fans. I thought it started out a bit meh but by the time they got to the Mushroom Kingdom, contrary to the OP, I pretty much forgot I was watching an Illumination film. Overall I'm really glad I saw it and will probably watch it again someday and would go see a sequel.

A kid in the audience cried when Bowser kidnapped Luigi and screamed in absolute terror during the Rainbow Road scene.