I agree with aaaaaa15 that, that would have made a very compelling and important statement, but Emma Stone is fabulous and I'm happy to she her do this.
Gabby, I don't think that everything needs to be about something political. La La Land chooses not to expore the horrors that are facing our nation and instead focus on two artists. Yes, they happen to be white, but I'm sure that's because they were the best choice for the roles. Also, to suggest that they are privileged and have no trials and struggles simply due to the color of their skin is a little ludicrous.
Also, between Moonlight and Fences, there is already quite a bit of diversity.