“Why shouldn’t everyone get an A if they all get the question right.”
Not sure how to say this gently, but if you teach a college calculus class and everyone gets an A, you won’t be teaching much longer. You can try and convince the dept head that your class is full of Eulers, Gauss’s, Riemanns, Hilberts et al, but they won’t buy it. Instead, they’ll wonder why everyone has signed up for your class and avoided the professor who gives the hard tests.
Calculus is a serious class with a lot of subtle concepts, not meant for easy As.