Welcome,
I will explain why as stated in the manga Itachi Uchiha is practically Invincible. There are two factors, his
GENJUTSU and his
LEGENDARY ITEMS.
Genjutsu:
Itachi's Tsukuyomi is almost a 1 shot ability, it has 1 weakness: If your target is blood related and has the Sharingan, he CAN break Tsukuyomi. This is a manga fact and was demonstrated by Sasuke. This is the only way to escape Tsukuyomi.
What this means is that if you are not blood related to Itachi, you must AVOID getting hit by Tsukuyomi or COUNTER it with a MORE powerful Genjutsu!
Chakra disruption DOESN'T work on ITACHI'S TSUKUYOMI! Why? Itachi is capable of manipulating the time of his Tsukuyomi (sasuke isn't), when you get hit by Tsukuyomi it STARTS and ENDS in 1 sec. 1 Sec = 24+ days if Itachi wants that.
People who can break Tsukuyomi:
1. Sage of the 6 Paths.
2. Sasuke Uchiha.
People who can AVOID or COUNTER Tsukuyomi with a more powerful genjutsu are:
1. Sage of the 6 Paths.
2. Madara Uchiha (Including Tobi Madara Uchiha).
3. Shishui Uchiha
4. Minato: Teleportation, by teleport spamming right away from the start he "COULD" (speculation) avoid getting hit by Tsukuyomi.
5. Guy: He is capable of avoiding Ocular Genjutsu by closing his eye (or looking at his opponents feet) and he is capable to fight his opponent.
Legendary Items:
Itachi's Susanoo is by far the strongest and most superior Susanoo we have seen in the manga for two reasons. It holds the
LEGENDARY YATA MIRROR and the
LEGENDARY SWORD OF TOTSUKA. This combination totally demolishes 99% of the Shinobi's known, kage's, sanins etc.
To be able to SURVIVE vs Itachi you must be able to DODGE or BLOCK Sword of Totsuka STAB attack, if it stabs you even in your finger it is a 100% 1 shot kill. Orochimaru and Ultimate Nagato were 1 shotted by the Sword of Totsuka. Because the Sword of Totsuka is a liquid ETHERAL Sword, you can't break or destroy it.
The only characters that can AVOID the Sword of Totsuga are:
1. Sage of the 6 Paths: He is the god of Naruto storyline, nobody can defeat him and he can defeat anybody.
2. Madara Uchiha (Including Tobi Madara Uchiha, they are the same): The ability to shift out of reality and teleport.
3. Minato: His yellow flash ability, Teleportation.
4. Raikage (s): Both the Third and Fourth raikage have the speed to avoid Sword of Totsuka.
5. Naruto KM: Naruto's yellow flash matched and out speeds the fourth Raikage.
*Common misconception: Nagato can only block the first Sword of Totsuka stab with his Shinra Tensei, then it will have a 5 sec cooldown.
To be able to land a lethal strike on Itachi you must somehow by pass the YATA MIRROR which reflects everything, the only way to do this is teleportation.
The only characters that can teleport and pass the Yata Mirror are:
1. Sage of the 6 Paths.
2. Madara Uchiha (Including Tobi Madara Uchiha).
3. Minato: While the Kunais can't by pass the Yata Mirror, they can surround them and Minato can teleport from every 360* degree and find an opening, Minato is more Intelligent than Itachi so he is capable of doing this.
So the be able to beat Itachi you must have BOTH the abilities to AVOID Blade of Totsuka and BYPASS the Yata Mirror.
Hope this enlightened you guys a bit