Honestly, in America these days, the only thing that can be used to measure success is the number of dollars that roll in. Coleman is pretty and black. People will tune in to watch based on that factor alone, but for those who aren't pleased by aesthetics, there's always the opportunity to watch and see if she falls on her face.
While being the same colour and having a similar appearance to the protagonist is important for any biopic, the true strength of whether someone will be believable in a role is their acting talent. Zendaya has shown promise in earlier roles, so I'm sure if she really puts her mind to it she will have the ability to bring Aaliyah back to life for the movie.
I believe Zendaya Coleman will be a great no not just great but an awesome Aaliyah. She look almost like Aaliyah if you look at her. I also think her acting skills are amazing and she will do a good job of shutting up the people that are talking trash about her.
As far as appearance I don't really agree with this casting decision because I feel they could have found someone who looked more like Aaliyah herself. Zendaya Coleman, from Disney, may have experience in the field and she will have the ability to own this role, but casting wise, I think a better job could have been done.