You have a good point and are probably correct, but still.
These days most McDonalds seem to have automatic doors and card payments are contactless via phone or card.
Assuming the kitchen staff keep their hands clean and the trays are washed the touchscreens are the most obvious thing too break the illusion of hygene.
The real problem I guess is eating food with your hands without immediately washing them first.
Historically before contactless payments and automatic doors the world didn't end so it probably is just a percived "yuck factor" on my part, I fully acknowledge that.
It's just... those screens and their suspicious smears... :-###..
