While it's true that the writers made a point to learn nothing about the franchise before writing it, there's an argument to be made that at that point there wasn't really much lore from the games. It came out in 93. If today they made a game where Mario and Luigi from our world follow Princess peach through a portal to save her from being kidnapped by Goombas, only to find Dinosaur New York and get jump powers from technology, then you find out Bowser has usurped the Mushroom Kingdom power structure by de-evolving the king to the point of him now being a fungus who spends the entire game gently helping Mario occasionally... That would be an amazing modern day Mario game. Forget Galaxy, that would be the most complex and interesting game in the franchise.

Plus, it's got the funniest joke I've heard in any movie.

Desk Sergeant: Name?

Mario: Mario.

Desk Sergeant: Last name?

Mario: Mario.

Desk Sergeant: (rolls eyes) Okay, what's your name?

Luigi: Luigi.

Desk Sergeant: (exasperated) Luigi Luigi?

Luigi: No. Luigi Mario.

The whole movie is a masterpiece and the twist that the king was the fungus that's been choking the city is great, and on re-watches you notice all the times the Marios are saved or helped by the fungus. It also implies that the convergent evolution of this parallel world includes both dinosaurs and fungus turning into basically identical people, and the mushroom people managed to become the ruling class.