I'm going to try to be fair. This movie is cute at best and unfunny at its worst. It has all of Illumination Studio's usual trademark humor, so if that sort of thing appeals to you, then you will like this movie. As an older Mario fan, it didn't appeal to me. I didn't think that it needed to force itself to be funny as your typical action-comedy hybrid that family-friendly films trend toward, but that's exactly where it failed to be a good Super Mario movie.
It's too busy trying to constantly entertain the audience with easy jokes, one-liners and the constant action that Illumination is known for that it lacks a Super Mario feel. None of the characters really felt like themselves, especially given that Charles Martinet was at the ready to record dialogue but he didn't voice either Mario or Luigi. Princess Peach lacks her cute, sweet demeanor (yes, it is possible to be cute, sweet and tough), and Mario and Luigi feel like anonymous heroes-in-training, not the brave and timid characters that Nintendo bring to life in their games. They didn't even feel like Lou Albano or Danny Wells or the Super Show cartoon characters. You can kinda see that's what they were going for in the first half of the movie. Nintendo show us who these characters are without telling, but this movie does the opposite and does a lot more telling than showing.
Bowser was the biggest disappointment. With the wonderful talent that was Jack Black voicing him, he could have really been an intimidating and formidable character like he was in Super Mario Odyssey, but this Bowser is whiny and insecure, like his character in the 1986 Anime "The Great Mission to Rescue Princess Peach!". It was a huge disappointment to me. Don't even get me started on that blue Luma prisoner that kept spouting its cringy, dark humor nonsense. That kind of fatalistic existentialism is extremely out of place in a Super Mario movie and it was easily the hardest part of the film for me to watch.
The visuals are stunning. The water swirling in the sewer drain scenes looks more realistic than in real life, and the Kong Kingdom kart scene is gorgeous, but that's where my compliments end. It does not make up for the poor narrative and a plot that is there is so full of holes that it might as well be swiss cheese. Sure, you may say "It's Super Mario, it doesn't need to have a complicated storyline", but It should have been a LOT better than this. It lacks the heart or moral that Disney's animation division and Pixar deliver, and the ending felt rushed and unfinished.
All in all, it's a generic family film in Super Mario clothing. It has a lot of effort put into it, but nowhere near the kind of creativity you'd like to see mirrored in Nintendo's usual standard. I hate to say it, but this feels like a lazy cash grab and one big advertisement for Nintendo. I think they allowed Illumination too much creative liberty, and it really shows as a nothing-special, just-another-Illumination-brand film that panders to a younger audience--not both new and old fans. I expected a lot more than this.