To state otherwise is to embrace the rule of faith. We creationists cannot scientifically prove Creation from observations of creation, we have to infer it from observed processes and from the results of processes unobserved in the past that happened after creation: The fossil record, geographic formation of rock layers, sedimentary deposits, observed changes in the speed of light (If this proves true). We also infer it from observations of decay that we can measure and compare it using the same method evolutionists use: uniformatarianism; Magnetic field decay, radiogenic helium, the lack of evidence of starting rates of K-AR, C14, and the like.
Either way, both systems rely on faith as regarding origins, but I believe only Creation is the accurate system that is proved through observed processes, and is the only rational answer for unobserved process results.
Evolution started as "How did we get here? Let's look at all the evidence and come up with the best answer that explains it." Creation started as "This book tells us how everything started, let's find evidence to back it up." The two approaches are quite different: the former is science, the latter is religion.
And, no, magnetic decay, attacks on isochron dating, and speed of light changes to the extent you're talking about (not true) do not show a young earth. They are merely attempts at making observations fit the Bible.
Surely you have overspoken here, possibly only through careless syntactic construction: You don't really believe that "creation" (bringing into being out of nothing, or without immediate material causation) is the only answer for "unobserved process results"? Read straightforwardly you would be claiming that no result without humanly observed (or confirmed?) causation can be rationaly inferred or preferentially supposed to have a natural cause. (E.g. the only "rational answer" with regard to the circulation of blood, before the action of the heart as a pump was observed, was that it was being done extra-naturally by God.)