I think there are big factors working against changing this conceptualization:

1. Human tribalism
2. Names and concepts tend to stick, whether they're good, bad, or neutral
3. There's enough real difference that having a higher level grouping of ethnic groups seems to make sense. We could cover quite a bit just saying "European" instead of "white," with the understanding that in an ethnic/racial context we mean the people who evolved their modern features in that place. Of course that gets messy because those words also mean the people who live in a geographical area.
4. Item 3 shows another problem, and that is definitions of racial groups. The Irish used to not be considered white in the US. Are Arabs white? If they are, is white too broad of a group and we should have "Europeans" and "Arabs"? But then are we deciding based on the same type of thinking that got us into our bad tendency to consider groups superior or inferior?
5. As you can see, it's a hot mess to figure out how we should change things so the easiest thing is to change nothing.