From a whovian perspective, the philosophy of Binti would be something like this - I can't accept Martha Jones, but Sontarans are cool. 
 One is often insecure about his stand when it comes to registering his like or dislike towards a culturally or ethnically diverse work. This often leads to a personally unjust review, under peer pressure or the fear of being branded by the adjectives for intolerance, non-progressiveness and their kins. I am unable to get my head around this old school racism or sectarianism, that forms the basic framework of Binti (also somehow limited to protagonist's particular tribe), considering the extremely diverse and pluralistic Intergalactic society, story derives it's universe off. 
 Okorafor is a really good writer, and I heavily appreciate the prose which consorted well with tribal girl narrative, and the non-pretentious word/world/culture building; but as far as science fiction is considered, story is solid meh.