Thats not quite true. I think most of the times students must realise that MBA is more about self learning. In some individual cases, it might be possible that a professor might lack skills to keep the students interested but a teaching profession is quite difficult as not only should a teachers concepts be sharp, he should be able to pass on the quality to the student.
Lately a lot of institutes have closed who have taken money but lacked teaching faculty. so i feel its the teaching thats most critical