It is not circular. It shows that if you know the derivative at x = 0 then you know it at any generic x. The derivative at x = 0 is a limit that is treated in all serious calculus textbooks. Do you expect W|A to give you all the steps up to the axioms of the real numbers?
I think that in this case W|A has given a pretty reasonable answer in this case. The limit Limit[(E^x - 1)/x, x -> 0]==1 is basic in every calculus textbook that I know of.
If you ask W|A the steps for the limit Limit[(E^x - 1)/x, x -> 0], it uses L’Hôpital’s rule, which assumes that we know the derivative of the exponential. This would have been circular!