He is disregarding how much effort and how many moving pieces are needed to have an employee with which you can order a sandwich and have it done the same way each time.
For starters you have to have ingredients ready, standard ways of storing them and much more. That is what Subway worked on for years to have standards and be able to hire someone to "make a sandwich".
OP disregards that people hired in McD or Subway get !detailed! instructions how to make a sandwich and which ingredients should be put in which type of sandwich. Then their workplace is optimized to do so.
List of ingredients is very limited as list of sandwiches you can order in Subway. List of ingredients in software is unlimited and there is no standard workplace and people imagination about what software to build is unlimited.
There is lots of magical thinking in OP comment. He would like to magically remove all those layers of abstraction and gives simplified example, that breaks down when you think about that example more than 1 minute.