But why would her being dead change anything for the better?
I don't know why they wouldn't use her, but I know one thing: the fact that they wouldn't use her has absolutely nothing to do with her mutant status or being Magneto's daughter. Even if this mini "fixes" that (uncertain) and even if it resurrects her at the end (uncertain), nothing will have changed for her at all. She'll still be a character who belongs on the Avengers and the Avengers office refuses to use.
Ommadon: “By summoning all the dark powers I will infest the spirit of man So that he uses his science and logic to destroy himself. Greed and avarice shall prevail, and those who do not hear my words shall pay the price. I'll teach man to use his machines, I'll show him what distorted science can give birth to. I'll teach him to fly like a fairy, and I'll give him the ultimate answer to all his science can ask. And the world will be free for my magic again.”
I assumed X-fans were generally tired of the Phoenix and wouldn't mind it disappearing for a while
I hope someone uses her, I'm just explaining why I (and other fans of Wanda, though certainly not all) have no hope at this point. I think they would rather write about the effect her death has on other characters than write about her. If her MCU stardom didn't change that, nothing will.
Odds are if Wanda comes back in an X-Book, Sins Erased in an X-Book, made a mutant again in an X-Book she'll be an X-Books character going forward especially since the Avengers don't want her.
The Avengers writers could still resurrect her whatever they want to, maybe in some years someone would like to use her again...