I like Jurnee Smollett, but Hailee Steinfeld was perfect for the role because her "real life ancestry" was a true reflection of the character she played, Mary.
Jurnee would not have been a good fit because when you and most people look at Jurnee you see a black woman and the whole point of her going out to talk to Remmick was to make him feel comfortable and assume he was talking to another white person like himself.
I know. Someone just said Jurnee Smollett and my mind just went a whirring at the delicious possibility. But you are right. When I see her, I don't see a woman that is 1/8 black and passing as white, something that I know is a reality for Hailee Steinfeld. That was actually brilliant by Ryan Coogler, as if the role was written specifically with her in mind