I think I understand what you are saying...but at the same time, given the example 6stringmerc used, there is nothing to "teach", the student has to practice more. That isn't teachable, the skill is only achieved via practice and work. (I give guitar lesions)

Which we, as a society, also seem reluctant to do. "oh you must not be good at that, try something else", instead of "if you want it you are going to have to work harder"