In the end, even a place capable of great burgers can serve you crap due to varying quality of their meat sourcing and the abilities of whomever is cooking that day. I wouldn't hesitate to believe that the work quality of someone making close to minimum wage doing a mind-numbingly awful position may not really care about the end result all that much.
I think the exception to this is McDonald's, which somehow has mechanized their training and cooking systems to the point where 99% of the time it tastes like exactly the same mediocre fare whereever and whenever you order