What does the strict avalanche criterion mean?
As pointed out in the comment, SAC is just one criterion relevant to diffusion, useful in ciphers as well as hash functions but by no means enough to provide security under any reasonable definition.

Just a partial list of desiderata for Sbox function design, optimal nonlinearity, high degree, low differential probabilities, high degree as a univariate polynomial, algebraic immunity, correlation immunity, etc should be enough to convince one of this.