That 1978 movie was made before blacks started feeling empowered, and now, with Obama and Holder and the many other black “leaders” looking for the slightest of incidents to cry racism, things could be different today.
It was the "black power" era, and numerous movies were made where classic stories were "updated" and re-imagined with black actors playing the roles. The focus of those films were usually tough black characters triumphing against "the man". The Wiz was the tail end of it, as it had started in 1971. In fact, many people think The Wiz bombing at the box office is what ended the Blaxploitation genre, as it disappeared in the 80s before they revived the idea of remaking white characters as black characters in the late 90s.
I'd say the difference between those black remakes in 1979 and 2014 is the latter were intentionally campy and entertaining. There's very little entertaining in the new "Annie"