Narutos weakeness is genjutsu remember when he claimed jiraiya taught him to break out then that fake itachi had him throwing rasengans at no one? This guy can't cast genjutsu and has show Little to no skill in defending against it. Think about it sasukes genjutsu is so strong not even the tailed beasts could break out so at the start of the fight a simple genjutsu and game over sasuke wins. Just saying
Genjutsu wouldn't have worked on him for several reasons.
1 - Naruto is a perfect jinchiruki.
2 - Naruto is more skilled at defeating genjutsu then you realized. Back near the beginning of part 2 when Itachi placed Naruto in genjutsu he had to attack Naruto emotions to stop him from defeating the genjutsu. That proves Naruto's skilled in genjutsu. If Naruto had little to no skills than Itachi (one of the best genjutsu users) wouldn't have needed to switch tactics.
Itachi has Naruto in genjutsu -
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Naruto relies on his training and began to defeat the genjutsu -
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Itachi switch tactics and attacks Naruto's emotions to stop him from defeating it -
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to
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3 - Naruto has improved alot since then and his skills are on completely different level. His chakra control has improved. He is one if not the best and is able to control, shape and manipulate all types of charka. Human chakra, sage charka, and tail beast charka. He proved he can create a rasengan with one hand without needing to be in sage or chakra mode.
4 - Naruto quickly noticed when Sakura was in genjutsu -
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