So because he doesn't possess a technique you've seen used against Obito in the manga/anime - means it is impossible for him to counter it? Because Kishi hasn't shown you that it's possible, you take that as fact that it can't be done?
That just shows you can't think for yourself.
In a manga it does mean that he can't counter it until shown otherwise. In fact, the whole "Itachi has intelligence" argument is null and void. A lot of opponents have intelligence. Danzo's guards, Fu and Torune were root members, so they had to have intelligence. Yet they failed horribly at figuring out kamui. Yamato has intelligence, but he didn't figure it out when that 8 man squad fought Obito either.
Just because someone has intelligence doesn't mean that you can automatically assume that they would be able to figure it out. That is why you have to wait until further notice.
Furthermore, arsenal is a key factor. Even if Itachi deduces the mechanics behind Kamui, that still doesn't mean that he has something to counter it in his arsenal. It is just like how part 1 Sasuke's sharingan was able to see Lee's kick coming, but that still didn't mean that he was able to dodge it.
Deduction is only half the story. Arsenal is the other half. I am saying that from what we have seen from Itachi's arsenal, he doesn't have anything that counters kamui (even if he does figure out the mechanics).
Plus, people bring up Itachi's intelligence as if Obito is some uneducated 5 year old. Obito is smart too. You act as if Itachi can be the only smart one in the battle.