Kakashi always starts the fight using his shadow clones/else, so it's not gonna end like in an instant as some people used to believe if they fight.Minato never uses much in a 1 vs 1 because he's already op. 1 on 1 most ninja would be skewered by Minato's kunai in a matter of seconds. kakashi wouldn't be able to hurt Minato as ftg is even more instant than kamui and I we all know kamui isn't nearly as strong without kuramas chakra boost.
He has enough time meanwhile to come up with his Kamui in action.
Deidara said that his doujutsu is Itachi's level anyway.
Unlike A Kakashi is smart enough to not let Minato dance around him with his kunais, don't ya think about that?