Firstly, Inhumans aren't just powered people like mutants. They're a millennia-old civilization with their own distinct culture, traditions, and societal hierarchy. Their entire world is designed to function only with terrigenesis and only with powers (from the lowest class to the highest). Terrigenesis is seen as the true form, the final form of life. It's their heredity and without the mists individuals would be deprived of heredity, therefore deprived of meaningful life as an Inhuman --not just deprived of life with powers. It's much more than that, and it's the most important thing in the entire universe to the Inhuman people. It's the one constant in a world full of variables. To suggest she would erradicate it without at least TRYING to find a neutral solution that would save mutants -and not essentially exterminate Inhumanity in the process- is not radical, nor should it be controversial. She is a Queen of an empire that's been around since pre-historic times and she cannot simply allow it to end because of what amounts to an insignificant blip on the millions of years old timeline of Inhuman society. The importance of terrigenesis must be measured with the lens that everyone in her society is powered, and thus they're not "super heroes" in the tradition, cookie-cutter sense. Inhumans are more than just people with powers, the powers MAKE the person.
Secondly, Queen Medusa absolutely does care about mutants and their plight. She left her husband and king, Black Bolt, because of the T-Cloud and the seemingly blatant disrespect of the terrigen he showed by using in as a bomb instead of as a birthright. The Inhuman people are split on the matter, still respecting their King but also feeling betrayed by him. This plays into mutants because they are embarrassed as a society to have caused the T-Cloud, and they are empathetic of what mutants are going through and feel deeply responsible (and guilty) for the current stage of mutant suffering. She has opened Attilan and every advanced resource they have to a mutant; Beast, in an attempt to resolve the M-pox and the cloud itself in a way that respects both sides of this argument. How is that suddenly viewed as uncaring? The fact that terrigen is considered the most sacred thing in the universe to be preserved by Inhumans at all cost is not news, it's been cannon since the 60's. Inhumans will do everything in their power to save both themselves and mutants (emphasis on the "and"), but you can't seriously expect Queen Medusa (or any Queen) to voluntarily allow for her people die off in the process.
Thirdly, if the shoe were on the other foot and mutants had accidentally poisoned Inhumans, of course they'd feel bad about it. How could they not? But they would not trade their lives (and the very existence of every mutants to ever come) in order to save Inhumanity and that's perfectly fine, expected, and acceptable. Why would they when they can seek out a neutral solution to appease all sides? That's what anyone would do. A bipartisan solution (like discovering a way to replicate terrigen, finding more terrigen crystals, or extracting the terrigen from the T-Cloud), one that doesn't kill off "them or us" shouldn't be controversial. The Inhumans have done nothing wrong, and while this senseless villainization of them does rile up the complex base, it's unwarranted and almost always factually inaccurate to the story or elements working in the real world, outside of said stories. Neither side wants anyone else to die! Medusa and Storm shared the notion that they're sick to death of all this death.