Creationism

It's a mistake to say "Either scientism or creationism." If those are the only two options, then of course a religious person must be a young-earther. But there is a third alternative: Catholicism. Scientism and creationism agree that if there is evolution, then there is no God. Assert God, deny evolution; assert evolution, deny God; or accept God & evolution.

Ken Ham

If you adopt Ham's interpretation for Genesis, you're committed to it for the whole of the Bible. All of his Protestant theology of sola scriptura and the infallible bible come into play.