This malaphor combines several thoughts, resulting in a humorous saying. Certainly “can’t cut the mustard” (one who cannot meet the required standard) and ” if you can’t stand the heat, get out of the kitchen” (don’t persist in a task if it is too much for you) are involved, but what about “if you can’t beat ’em, join ’em”? Also let’s not forget “who cut the cheese”? (who farted?) Given these idioms and sayings, I think it is more appropriate to say, “if you cut the cheese, get out of the kitchen”.