Contrary to what you may think Creationism is not the alternative to evolution, but rather it is the alternative to Naturalism. This confusion has often been used to argue against the scientific nature of creation science. This distinction is very important to understand the difference between scientific theories and their philosophical underpinnings.
When you are trying to understand the regular functioning of some aspect of the universe in the present, such that it can be tested or observed, then the differences in these philosophical presuppositions are insignificant since this is by definition what a natural phenomenon is. However, when you are looking at a past event that is either reported to be supernatural or for which there are other reasons for attributing the event to supernatural agency, then the differences between these two philosophical presuppositions will be significant. Furthermore, if an event was indeed supernatural in nature and you try to describe what happened based on absolute naturalism, you will not get the right answer. The problem with philosophical naturalism is that it makes it impossible to conclude that an event was supernatural regardless of the evidence.
Under philosophical naturalism, only natural processes are considered to exist. A supernatural agency such as God is excluded from consideration before any evidence is even looked at. Sadly, now methodological naturalism has been used as a way of pushing naturalism in practice when doing scientific research. Whether one’s naturalism is philosophical or just methodological the result is the same. They exclude God as a possible explanation for anything regardless of the evidence. This makes it impossible from mainstream science to see any evidence for the Genesis Flood, that is it is excluded as a possibility because it is not possible under naturalism.
What Creationism and Naturalism have in common, from a scientific perspective is that they are both philosophical starting points for the development of theories. Naturalism excludes supernatural agency by definition, while creationism allows for it and considers the possibility of supernatural explanations when the situation calls for it. Both are philosophical starting points that are then used to develop theories that can be tested.
To properly understand this discussion, it is important to realize that creationism is not an alternative to evolution but an alternative to naturalism. There is a difference. Once you understand that both creationism and naturalism are philosophical positions rather than scientific, but they are both used as a starting point for scientific theories then understanding the difference between the conclusions of creationists and evolutionists becomes a lot easier.