You will have to put a bit of work into thinking about it, if you don't already see it. At the risk of being more rude than effective, I spelled it out pretty c

You will have to put a bit of work into thinking about it, if you don't already see it. At the risk of being more rude than effective, I spelled it out pretty clearly above if you understand autodiff, which requires an understanding of the chain rule, which most people first learn about in a calculus class. If you want to claim that autodiff is a replacement for all our differentiation needs, then you should try to understand when it doesn't work.