Whats not manga supported?
Your missing the point genjutsu is a technique that hashi no feats of resistance too. Even Itachi simple genjutsu techniques affect experienced users case and point Oro.
Why are you comparing Orochimaru, to Hashirama?? And SO6P has no feats of resistance to genjutsu either.. does that mean he can't break it?? no.
Genjutsu was shown 2 ways to be broken: The person disrupts their own chakra, which you need to be very powerful for. AND somebody else can disrupt your chakra.
^^^^^^ That my friend was stated by a character who has much more experience with techniques.. and much more knowledge. And that character was teaching Naruto Uzumaki, how to break genjutsu, in case he encountered a genjutsu user (direct reference to Itachi Uchiha). So Tsukuyomi is no exception from being able to break out of it, via those 2 methods.
What is Tsukuyomi in a non-hyped/exaggerated form: A genjutsu/technique avalaible to Itachi Uchiha , that grants him the ability to control and have a very strong control over his opponent's chakra in the brain. In essence, it is a genjutsu that is very powerful (this is no fan-fiction, but breaking down the technique for it is).
Why Sharingan is the best way/easiest way to break it: The sharingan is unlocked when a special chakra is unlocked in their brain. Meaning their eyes provide the best control over the chakra in the brain (which is used to cast genjutsu), since the sharingan is directly connected to the chakra in the brain. Thus making it easier for those who possess the sharingan, to counter genjutsu.
HOWEVER, this does not mean all sharingan can counter Itachi's tsukuyomi. Because at end of the day, it comes down to power. Is the person's sharingan strong enough to control the chakra in their brains or no and disrrupt the flow. And how do you gain a powerful sharingan?? powerful chakra. So at the end of the day it all comes down to chakra, and the mastery of control.
Itachi's opponents who he used tsukuyomi on:
- Kakashi hatake, he neither possesses the best chakra control.. he doesn't possess natural sharingan chakra... he doesn't possess huge reserves.. he is automatically out of the options of people who can counter him.
- Orochimaru, hes never shown perfected chakra control .. hes also never shown strong chakra like Hashirama or Tobirama.. So hes already out of the options as well.
- Sasuke Uchiha , he possessed stronger eye power than Itachi aka able to counter Itachi's control on his brain's chakra and interrupt the flow..
Now you're claiming, Itachi can use this technique on people who have monsterous chakras, and have very good chakra control.. and crack rooms with just by raising their chakra .. while having no feats of Tsukuyomi being used against people like them.. Not only that.. you also don't have any feats from Itachi using tsukuyomi on somebody like Tsunade or Sakura who are stated to possess the best chakra control....
But you expect people to believe and throw away the logic of how genjutsu can be broken.. because a character's (who has limited knowledge) statement from part 1 and, because hes been successful with that technique against people who aren't really the most skilled to break his technique??
I'm sure you as an Itachi fan have realized by now, how much Itachi's character has been "protected"..