Can't believe I actually agree with smd, but kamui is overrated to high hell, Kakashi tried to use it on obito instead of Maddy even when he KNEW obito had kamui himself. it pretty much proves that the jutsu has limitations and kakashi is aware that if he tries it on Maddy it's wasted chakra.
ppl like to pull the feat of kakashi kamu'ing those two susanoo arrows as proof he can use it on anyone within an instant but anyone with an inkling of basic physics knows that's just bad logic, the susanoo arrows flew straight at kakashi, that's like flying a rocket ship on a direct course straight into a black hole, of course he'd be able to make them vanish, they flew straight into the black hole/kamui.
ppl also like to claim that Naruto's BM clone was hit with kamui so he was able to hit anyone since ppl assume the clone was moving at top speed. that's also dumb logic because it was all apart of the plan for the clone to get kamui'd, in the actual scan you even see Naruto looking back at kakashi as he goes towards obito so it was all a part of a coordinated plan, pretty much like any major thing kakashi has done with kamui.