kakashi was testing his sharingan. he wanted to see if he was strong enough with it to fight back MS genjutsu. itachi agreed kakashi could fight it so he put him in tsukoyomi.
remember what happened last time itachi and kakashi fought? although itachi said he couldnt use tsukoyomi he said that kakashi's timing was perfect. even with the sharingan itachi couldnt see kakashi's shadow clone. and itachi was always said to have been a true heir of the sharingan. all that was said about sasukes was that his sharingan was keener. meaning it will surpass itachis eventually. sasuke still isnt itachi's level.
oh and you think kakashi couldnt follow sasuke if he moves fast in unpredicatble way? what is it that the sharingan does? oh yeah predicts movement. it doesnt matter how unorthodox you move it will see it.
oh and look at what kakashi said again. he does say they are both getting stronger yes. but we know that nauto is more powerful than sasuke. naruto is on a whole new level atm. sasuke is almost at kage level. i know he is fighting all the kage but atm he has only fought one then pulled out his trump card as a distraction to get away from 2. and sasuke although he can take what the raikage dished out, sasuke could not beat him. in fact he almost got killed. sasuke is powerful yeah but not that powerful.
you have a look at sasukes chidori and most of us know that kakashi's lightning blade is more powerful than chidori. also kakashi does have a sharingan so my theory is that kakashi can beat the raikage. sasuke managed to just get through the raikages armor a little. if kakashi did that it would have gotten through. not only that but kakashi is smarter, faster, and has better jutsu(imo).
and thank you about me being your worst enemy