It's normal that people from different ethnicities find another's typical trait unattractive.
We're programmed to go for the ones who are the most like us, that's what we know, what we grow up with, usually.
Inter-racial couples are an exception, there aren't many out there.
Traits like the single Asian eyelid is seen as foreign and strange to Caucasians or Africans.
A ghetto booty is very appreciated by African-American males, while other cultures and ethnicities will find them very unattractive.
As a species we're xenophobic by nature, you can only fight it to some extent.
Some of it is genetics, some of it is exposure and upbringing.
You can't help what you like and don't like, but it doesn't hurt to give people who are outside your usual "attraction-zone" a chance if you like them personality-wise, often looks will follow.
There is no "universally unattractive ethnicity", just different "races" who tend to go for others of their own rather than some who look nothing like them.
I'm Caucasian and don't have any black friends. I had 2 black classmates in school, otherwise no "exposure" in that aspect.
The media I was exposed to on the other hand showed me sleek glossy silky hair in all the hair product commercials from a very young age. There were never any black women in those commercials, because they weren't the marketed target.
I have been trained to think that such hair is what is considered beautiful where I live.
In contrast an African woman's hair is very strange to me - but that's the key, not strange, period, but strange TO ME.
Beauty in the eye of the beholder is right, it's a little more controlled than the saying might suggest, though.