I am not even sure this is the right DD.
When you have a long line in the mornings, and they must know that in the mornings every second matter, they must learn how to speed things up, and let people go on their way ASAP.
Leaving the slow service aside, the place is clean, and they make good coffee, and it is my preferred DD when I need a coffee before entering the freeway.
Dunkin's shouldn't be super heroes, just to make good coffee as DD knows, and make it quick.