I've come to the conclusion, to see that Itachi is not a perfectionist(EDIT: Scrap underlined with perfect). He is indeed a skilled, overpowered, smart and intelligent shinobi, but not perfect.
Itachi is known for always being the shadows, having a backup strategy, and succeeds in the failing look.
Itachi is overpowered, Yata and Totsuka, Amaterasu, Tsukiyomi, extended sharingan duration. This is only in terms of unique abilities.
Itachi is smart, He looks like he's calm, and in fact he is calm, having backup plans.
Itachi is considerate, thinking to save the village since he was a kid.
Itachi feels remorse, regret, and can hide his emotions. A human!
Itachi can do well in his strategy and almost if not always succeeds because he gets inside the enemy's head.
But where he was proven to be wrong, is in long plans, which seems like he done it good for people to think he's still a villain. But didn't make his brother what he wanted, as much as he tried, Obito ruined everything, and after he told Sauske, Sasuke still wasn't sure if should still protect Konoha or not.
So yes a human, tried his best, done his best, failed in one thing. And a loner worker.