We used the buses along with various other Disney transportation during a prior visit and it worked fine. Sometimes a bus had just departed and we had to wait a few minutes for the next one, but others times we boarded a bus and it soon left for our destination. I think some people are impatient and think Disney transportation is some sort of personal valet service which it was never intended to be. Clearly if you exit MK after the fireworks, it should be no surprise MANY others are also leaving and you will have to wait your turn for whatever form of transportation you choose.