Why has service declined in the past decade? Teenagers have worked in fast food since the 1950's and are not lazier or stupider than in the past.
Ask any of the teens that work in food service if they aspire to become managers. The overwhelming response will be "No." because the managers they work with have shrugged and so have their predecessors. There are few competent managers and those are worked to death (Tyler et al) to make up the deficiencies of the other managers and workers.
If the reader has wondered why it takes so long to get their order or why the order is "always" wrong, or why items are not available, then you admit, perhaps unknowingly, that Atlas has shrugged.
Taking what has been learned from your food experience and apply that from small to large businesses and you will know that no one wants to be responsible for the incompetents below them. Eventually, they just quit, i.e. shrug or they stay only to receive a paycheck (not to work per se).
These can be considered zombies in training, since they had brains at one time or they would not have gone into positions of authority.