What does creationism lack that makes it not a science? Everything.
1. It lacks any mathematical models, even something as simple as Mendel's
laws. When creationists do attempt some math (as in their probability
arguments) they produce rubbish that should embarrass a high school
2. It has no basic argument that gives a unified explanation of a variety
of phenomena. The closest candidate is Noah's flood. But for a flood
to produce phenomena, by "hydrodynamic sorting" or whatever, it has to
work by physical processes that have observable consequences and
mathematical models. The detailed analysis that is the hallmark of
real science is absent.
3. It lacks any contact with any science. It is in conflict with biology,
paleontology, geology, physics, and astronomy at all points.
4. It does not make predictions which are testable. The essence of
creationism is that the world is the way it is because that's the
way god made it. This makes no prediction about the outcome of an
experiment and any result is consistent with the theory.