Let me define what I mean I by plain: burger, bun, and possibly cheese depending on whether you asked for a hamburger or cheeseburger.
Now, I won’t knock someone for liking lettuce and tomato and all that stuff on a burger. Moreover, those should remain as options. However, they should be just that: options. The current state of ordering a burger is akin to ordering a pizza and having Hawaiian or Everything pizza be the default instead of cheese. There’s a reason cheese is the default! The default should be the most basic version of a food, with the options being things that add more toppings onto it.