Exactly how serious, gritty and straight laced can a game about a plumber fighting a dinosaur turtle to save a princess of sentient mushrooms be?
The repeated plot over and over again more or less intentionally made the series more cartoony as bowser went from "Serious thread" in the first one, to ineffectual and jealous as shown by more and more failures...
and ESPECIALLY established by Mario RPG.
Essentially the repeated nature of the series established that this is some kind of "working norm".
Also... if such a thing bothers you... that's really more of a personal issue, then universally alienating
To quote CS Lewis.
“Critics who treat ‘adult’ as a term of approval, instead of as a merely descriptive term, cannot be adult themselves. To be concerned about being grown up, to admire the grown up because it is grown up, to blush at the suspicion of being childish; these things are the marks of childhood and adolescence. And in childhood and adolescence they are, in moderation, healthy symptoms. Young things ought to want to grow. But to carry on into middle life or even into early manhood this concern about being adult is a mark of really arrested development. When I was ten, I read fairy tales in secret and would have been ashamed if I had been found doing so. Now that I am fifty I read them openly. When I became a man I put away childish things, including the fear of childishness and the desire to be very grown up.”
