I think the value add in Five Guys is in the fries. Apart from the obvious generosity of the amount of fries they give you which completely dwarfs any other restaurant, they go through a serious effort making them taste really good as well. They soak the cut potatoes in running water for 5 hours before frying them in peanut oil with a special double dip method to give a good consistency of fluffy on the inside and crisp on the outside.

I agree the burger itself is pretty mediocre for what you pay. The “all ingredients included” mantra also encourages people to make burgers that fall apart as you pick them up. There’s also nothing really special about it - the company even actively advertises that they use common big box grocery vendors to source their ingredients and anything you eat there is mostly available off the shelf at your local grocery. When I worked there all of our stuff came on a Kroger truck.