even in the link you sent they have a computation for raw QBR.

Not a usable one. I cannot calculate it using that formula. It says in the article: "For example, a 1st and goal chance on the opponent's’ 1 yard line heavily favors the offense, yielding a positive point value. On the other hand, a 3rd and 9 on the team's own 3 yard line is heavily negative because it drastically favors the opponent."

That means jack squat. I can look at my database and see a play that was 1st and Goal on the one yard line. I still cannot use that to calculate the EPA.

Even if I could, then I run into this: "The Expected Points Added (or lost) in each play are divided among the contributing players on the field based on the role of each player and the type of play. Deeper throws give a higher share of credit to the QB, while screen passes give relatively less credit to the QB and more to the receiver."

I have no information about what percentage of the credit is given to which role during which play type. I have no need or use for a prose-based explanation. I need the formula. The article says it takes 10,000 lines of code. No problem. I can write 10,000 lines of code.

Going back to your restaurant analogy, I don't want "then we baked the chicken." That has zero value to me. I need to know the temperature and duration. There is no mid-range. Unless I know everything, then I know nothing. QBR is, therefore, worthless.