Creationism is a belief, classified as a philosophy. Good point cosmology, geology, archaeology and the rest are science. The fact of a rock cannot argue aganst a belief such as creationism. The fact an organism evolves is not an argument against creationism. Now, the inductive reasoning from the fact of evolution can be used to make a case against creationism. Fine. But that isn't the unassailable position the fact of a rock is.
Darwinism is the opposite philosophy of creationism. Darwinists think their reasoning unassailable, any attack in their beliefs is an attack on science they say. True enough empirical science is unassailable. But what they're selling isn't empirical science, its philosophy.