Nah, Itachi has the sharingan and will see Kamui coming, and be able to react (sharingan let's you predict people's attacks, even to the point of letting Sasuke go toe to toe with A or B). He's faster than Itachi too and if bloodlusted, and they're both going all out, he strikes first. This is bad because Kakashi has to look at Itachi to pull off Kamui, and Itachi can instantly genjutsu him if he does.
Not to mention Itachi can dodge as he sees it coming, and as Kakashi is reacting to look at him and use it, he can have the Yata Mirror out, or have switched with a clone (as he repeatedly does in fights with nobody noticing, or have Ammy'd him, etc, etc). This is where being slower and less reactive hurts Kakashi, who is underrated... just not in this fight. His big advantage is in opponents without the sharingan (who can't counter react to his predicting their reactions), or against characters who can't counter his Kamui (and are faster), like Rinnegan users who can suck it up, or space time users who can circumvent/counter it. Or characters for whom the no-feat limit kicks in.