This game has very high ups when talking about the gameplay, but very (and I mean VERY) low lows. It doesn't help that it comes from one of the greatest RPG sagas that Nintendo has ever created.
It's story is bland and uninspired, the unique character designs are mostly gone (with the exception of a familiar yellow star spirit) and the mix between franchises isn't very special (it mostly plays like a regular M&L game).
Surprisingly, the gameplay is the best in the franchise so far (really cool and quite difficult to master bros. attacks and trio attacks mixed with a little of RNG from the new deck building mechanic that helps you in combat), and the music is on par with the other titles in the series.
Overall, a missed opportunity to make something truly great and unique with two peak RPG franchises as Mario & Luigi and Paper Mario are. Really hoping for a sequel that could fix all these problems.