I think that's why the idea of a protected class has typically been central to US legal definitions of equality: application to every individual characteristic

I think that's why the idea of a protected class has typically been central to US legal definitions of equality: application to every individual characteristic is untenable, but blindness to all impinges on justice too. Or in essence, how to address the historical inequities of racism and sexism, without also ushering in something ridiculous like "mentalism" that attempts to help people who are "bad at tests and grades."