Her back story is just as good as any other major super hero and her look, especially in the new comics is very easily readable and simple while still being different enough from other hero to be instantly recognizable. I get that taste is subjective and not liking her design doesn't make you wrong but you can't argue that it isn't well designed
As to the main appeal of her, I don't think they went hard enough in the movies but in the comics it's the scope of her powers and what that means. CD is easily one of the most powerful players from earth but she . This is someone who's able to manipulate not just heat and gravity but also absorb magical energy travel faster than sound or create the power equivalent of nukes with her hands.
Even with all this power though, she can't just stomp her way through the universe and that illustrates just how big and intimidating the universe of marvel actually is.
In a similar way Deadpools ability to break the fourth wall and operate with in meta-mechanics of the story, her character insane abilities over physical limitations just opens up possibilities for new stories that characters who need a more limited power set just can't. I really hope they play up how insane her powers are and how the fact that she can't stay on earth all the time means there's much bigger fish to fry.