The essay is meant to describe how fast-food came into being and how it has changed since that beginning. It also works hard to describe the amazing level of "sameness" that is desired by consumers and the way that appeals to people who are eating away from home.
From its beginnings as a public-house type of establishment that served the same thing which came to be called an "ordinary," to its current form as a franchise of a place like McDonalds or Burger King, the fast-food establishment derives is utility from sameness, that the consumer can expect the same thing no matter where they find a franchise. The prices should be manageable but the most important aspect is meeting the customers expectations of sameness.
The essay points out the ways that a current fast-food franchise must deliver a very complex set of tastes and textures to a very picky consumer but all of that complexity is hidden so that the customer simply orders and then gets what they expect.