Contradiction

A lot of people are looking forward to the movie version of Dreamgirls, but one thing (at least) bothers me. David Denby's New Yorker rave mentions a contradiction without indentifying it as such:

[Director] Condon pursues two tracks: he celebrates the chart-topping success of groups like the Supremes, but he makes it clear that what they have achieved, however exciting, is not the same thing as artistic success.

In other words, we're gonna get to watch a bunch of numbers that are not artistically successful. Can that be good?

By the way, the Supremes were artistically successful.