To the student this is just a blind alley. With luck the course will make some sense at the end. Because it is so hard for the student to see where preparatory exercises are leading the instructor has to take extra time handling each student's confusion. Very often the lesson clarifications have to include showing the student a context in which this lesson fits. This can be changed with an approach which originates with goals.
Goals provide a context.
The goal-centered approach doesn't get rid of the instructor's knowledge. It just re-arranges the order in which that knowledge is applied. The effort which now goes into designing preparatory exercises goes into turning those exercises into a resource bank. The resouce bank contains both project hints and course content. With a resource bank the teacher can turn the students lose to solve a goal that both instructor and student can see.