An appealing analogy but recipes have defined testable outcomes. You know what a Victoria sponge is supposed to look like (there's probably even a picture of one in the book). You can perfectly evaluate when a substitute has ruined it.

Agile doesn't have that, there is no functional equivelant of "the cake should be moist and rise evenly". What does "Agile" adoption look like? Faster delivery? Happier Developers? More revenue? Fewer bugs? This is never defined up front and they shift depending on the person being asked. This means you can never actually determine if someone "left out an essential ingredient".

The irony is that Agiles own favoured development practice (TDD) cannot be applied to Agile itself. There is no acceptance test for the process, you can't iterate on something that isn't measured and has no defined outcome.

/r/ididnthaveeggs works because everyone agrees on what the dish should have been.