The big guns of ID like Michael Behe, accept common descent as a given.
Denton, author of "Evolution: A Theory in Crisis," believes in fine tuning, the idea that the universe was set up at creation to produce evolution. Denton's ideology is one hundred percent compatible with mainstream biology.
I haven't been able to figure out why creationists think ID supports a young earth interpretation.
It is because they think the Bible says so and therefore it is, QED.
and this is why ID is ridiculed by scientists.
"I haven't been able to figure out why creationists think ID supports a young earth interpretation."
Creationism...i.e a literal interp of the old testament, is a different version of "Intelligent Design." The two get mixed up frequently and this causes endless and meaningless exchanges between ID folk and Darwinists. Creationist ID is the straw man used by Darwinists to dismiss all ID.