This movie adds to the pile of bad video game movies. The worst thing about The Super Mario Bros Movie is how they handle the characters. Here's why:
Luigi: He is incompotent, useless and too reliant on Mario and is barely even in the film. This is shown by how Luigi keeps crying for Mario in Bowser's dungeon and even before that, looks at Mario as his one and only saviour as if Luigi isn't meant to be a partner/sidekick to Mario. What a loser.
Bowser: The movie flanderised Bowser immensely. Basically, his apparent crush on Princess Peach is diled up to the max where it becomes cringy especially during his song. His hatred of Mario now stems from jealously over Peach. The film tries to portray Bowser as a threatening villain but he comes off as a complete joke. Bowser is now only really evil because of his crush on Peach. Stealing Power Stars, sacrificing prisoners and even killing a Koopa Troopa who asked if Peach would say no was all because of Peach. Canonically, the real Bowser just straight up forced Peach into marriage.
Mario: He really shouldn't have been in this movie. Mario's whole cliche shick was that he is a doubted hero that everybody treats as some loser but he becomes great. This is shown when his family scolds him for his advert and being a bad influence on Luigi, Peach mocking him for being short etc. Illumination made the plot bend in favour of Mario. For example, he gets plot armoured out of dying by defeating Donkey Kong with a cat suit which started because he making a deal to fight DK. Secondly, he causes his team to lose and then gets eaten by an eel but somehow finds a way out. Additionally, Mario broke the magic pipe which sucks everyone into his world, runs away from Bowser to reach the Super Star but gets saved by Luigi when he should died since Bowser's fire was about to hit him. After this he gets some stupid late minute motivation because Bowser calls him worthless and teams up with Luigi using the Super Star and ends up defeating Bowser. You can see the problem here. In conclusion, Mario felt forced into a role to an extent where the movie had to plot armour him in times where he should have died. Even during the first time Mario meets Peach, she tells him to complete a training course which he fails at but Peach just lets him join her team because Mario almost succeeds.
Peach: She was a wannabe Samus Aran who may as well have been the main character of the movie since the plot forced her to harbour Mario.
The dialogue in the movie was full of cringy jokes and references.
The pacing as well was awful. Many plot points and and elements needed proper build up such as Peach and Mario's relationship and DK and Mario's sudden frienship. The movie felt the need to rush itself and play safe, along with the movie lacking high stakes and intensity.
The voice acting is still mid. The fake advert scene had Chris Pratt actually do a decent Mario impression.