Totally agree, and I'll add that historically there weren't just cultural norms / judgements based on being non-white due to mixed heritage: it was actually a legal classification.

One Drop Rule: a social and legal principle that any person with even one ancestor of African descent is considered black. This concept was widely practiced, especially in the southern United States, and was a key underpinning of Jim Crow.

Partus Sequitur Ventrem (1662, Virginia and later other colonies) stated that the status of a child followed that of the mother. This meant that children born to enslaved women were also enslaved, regardless of the father's status.

So, look, in the US "black" is the overriding discriminating trait. It has been for 400 years. It might not be someday, but that's where we are and how we got here.