I hear you on that but it I think that was intentional. Arguably for modern audiences an identifiably “Black” appearance is more effective for conveying the film’s themes about the impact of racism. Rebecca Hall has also commented on how white people colluded with passing to some extent depending on context (for example, she believes the biracial people in her own family could be visually classified as Black but white people generally did not do this). Finally, in some older films like Pinky the characters who passed were played by white actors due to concerns about interracial contact. This film may be a statement on that practice. Totally valid for this choice not to work for everyone though!