The worst part for me by far was the "remember this trendy pop song?" soundtrack and pop-culture references that weren't necessarily Nintendo references. I gave up midway through the movie because these made me cringe.
Also, Peach was your usual, modern movie Mary Sue.
And how does it fare if you don't add the "its for kids" label, to lower the standards?
I mean, we used to have movies that were good enough to not have to even mention this. Toy Story, Aladdin, Lion King... I don't remember anyone ever having to lower the standards to justify those.
If you watch the movie with your kids, having introduced them to Nintendo previously it will be a great deal of fun. The references are spot on, it looks and sounds great and has a sense of humour all the family can enjoy.
It is better than 95% of kids CGI movies. I know as I have suffered through hundreds of them multiple times. Mario is not as good as Shrek 2 (the goat in my book) but is far better than Dispicable Me, Frozen 2, Sharktale etc.
Applying standards of absolute classics such as Lion King / Aladin is just as troublesome for modern Disney as anyone else. But even they are taken as "kids movies", as the script (how they try to engage the whole audience), performances (effort considering it would rarely be an artists defining role) and visuals are all taken in that context and are all held up highly today as they exceeded expectations of a kids movie on all those fronts.
The joyless Mario was had back in the day, it was more gritty, more adult and a truly fucking grim film. A travestly second only to MJ's Moonwalker.
The success and acclaim may partly be due to the slate of dross being pumped out the last few years and a competent fun family movie being a welcome relief; but even if this came out around toy story it would still have been a huge hit.
Parents, I recommend this movie.