behind the counter-guy, in that wide silver opening, is a black plastic slope with with burgers queuing up. The cooks are constantly cooking, even when nobody has ordered anything, and that means they can get the efficiency boost of making 5 Big Macs at the same time - laying out 5 boxes, 5 buns, 5 patties cooking, etc. - and with no customer waiting on them, there need be no immediate rush[1]. The cashier only picks one up and puts it on your tray, much less than 60 seconds and no stress[1]. Contrast with Subway where the cashier has to assemble one custom sandwich at a time while the customer and queue of waiting people all watch (stressor); they can not get custom sandwiches into muscle memory, or the efficiency of doing several at once (slow), and the cashier delaying for a moment doesn't relieve pressure by letting the buffer fill, it just adds more pressure.
If McDonalds is now taking 5-10 minutes for a typical order, what has gone wrong with their fast-food-factory-production-line design?
[1] Maybe it isn't actually low stress or no-rush in McDonalds, but that design of food service could be.