What purposes- Does it come with a built-in sandwich maker? Even Obito's Intangibility Initiation - arguably and by canon a much superior version of Kamui - failed before Amaterasu. Since Amaterasu Spawns on the target, he isn't Kamui-ing anything away. It's pure fanfiction.
You are gauging a mortally sick Itachi's performance against Kakashi? Even in that condition he was constantly using Genjutsu at start, used several Crow Clones, used Amaterasu twice, and the second time for quite a while by making the spawn point follow his line-of-sight so that the entire neighboring trees were engulfed in flames. Then he used Tsukuyomi, an advanced Katon attack twice, Shuriken-Justu, several high-speed parries, and then V4 Susano'o, which he maintained for quite some time. Here are your actual facts.
Kamui can be dealt with Amaterasu or Tsukuyomi, as it's all about quick draw here, and Itachi and any Uchiha would have a faster one.
If he could kamui a sage rasengan that hit him b4 it even damages his clothes he can kamui ama.
If there's a sandwich maker in the kamui dimension then.... yes yes it does.
Genjutsu's cool.
Crow clones cost less than shadow clones but whateves
2 ama
1 tsuki
Grand fire ball isn't really advanced. Wave arc sauce was using that.
Shuriken jutsu? No sir all he did was throw shuriken. That's not a jutsu.
1 susanno.
5 ms tech's and a flurry of other stuff
While kakashi pushed out
5 kamui of varying sizes( gedo mazou head?)
4 raikiri's
2 raiden's
2 raikiri's ran on ninja tools.
2 shadow clones costs more than crow clones but hey
Earth wall. I feel like I'm forgetting something but I'll leave it at that.
How does ama or tsuki deal with kamui? They don't check or counter it.
And no itachi even as an edo required time to pull out ms, and more time afterwards to use the techniques.
Kakashi does it in between panels.
So yeah.