Magic isn't as big as other mahou shoujos, therefore "plot of the week" episodes aren't hindered by Monsters of the Week.
Speaking of which, it has no Monsters of the Week. Magic is sometimes used to help, but not to the extent where everything is fixed. Sometimes nothing is fixed, and thus they have to rely on their humanity to solve a problem. So right there alone makes it not like other mahou shoujos.
That and considering the general age of the characters that get exposure, it explores themes rather maturily. Like... lets compare it to say... an M-rated game. Despite being colorful as fuck, Doremi beats them handily here.
The show does not exist just to primarily promote the main characters, the anime dedicates itself to flesh out its characters, from their teachers, to students, to parents and even to the witches. There's also the whole flesh out the world bit over the course of the show, and each season basically focuses on a specific theme, and explores that very well (ie. # is all about parenthood).
It frankly needs more promotion.