It's so weird to me that people still call Mia morally gray

She wasn't morally gray. She was evil. She knowingly and intentionally worked for a terrorist organization that created bioweapons. She wasn't low ranking either. On top of that she was very involved with the Eveline project to the point that she was the mother. We find out later that Eveline was a HUMAN FETUS that was then infected with mold or whatever. That is evil, full stop. Then on top of THAT we know that she lied to Ethan about being a "nanny" when everything went sideways and she disappeared for three years. And what's worse is that we don't have any real confirmation that she ever came clean to Ethan fully.

And no, not wanting your loved one to die doesn't make you morally gray, it makes you an evil person with people you care about. I can come up with a list of people our entire world believes is evil and then list the people they loved for you. Loving a person doesn't make you not evil, it makes you human.