I understand what you're saying, but exposing our children to a variety of media representations does matter. So I am very glad to see an African-American princess added to the Disney line-up. As an African-American woman, I can attest to the importance of seeing images of beauty that reflect you growing up. I was a kid who was very into fairytales, princesses, Barbie, etc., growing up and my parents had a hard time finding stories, dolls, etc, which looked like me. I am glad that this is changing so that when I have children, they may be able to choose from a true spectrum of images.
On the other hand, I am not particularly bothered by the new prince. White, Hispanic, Mediterranean or otherwise, I think the choice is actually a surprisingly forward move on Disney's part. If the Prince is actually supposed to be Black, it seems that Disney is recognizing that Black people (or any other race for that matter) don't all look exactly alike. If the prince is supposed to be of another race, it acknowledges the many multiracial families in the U.S. Additionally, when we do see these infrequent representations of multiracial families and relationships in tv and film, it is almost always a Black man and White woman. This variant shows that the reverse does occur.
Coming from a girl whose favorite Disney character growing up was Alice, I have nothing against the early princesses, but I am very glad that Disney is finally making an effort to have a more well-rounded pantheon of characters. I hope they continue in this vein to include not only more racial diversity, but also social diversity, diversity of ability and other circumstances. All children deserve to see aspects of themselves reflected in the media.