I can't say that I didn't enjoy the remake - it was very well done. Choosing Mos Def as Ford Prefect worked out pretty well also. I don't even fault them for changing things - because Douglas Adams changed things between versions, the TV show, and his authorization of the movie - he did it on purpose.
I don't think this particular instance was intended to replace a white person, I think they just wanted someone who could be funny in the role.....