WARNING: The following contains spoilers for 86-Eighty-Six Episode 11, “Here We Go,” now streaming on Crunchyroll.
One of the most revered, emotional arcs in the Naruto series will forever be the Uchiha rivalry between the brothers Itachi and Sasuke. The former was initially assumed to be a villain working with the Akatsuki and the man who ultimately ended the clan, which drove Sasuke to break bad and hunt him down.
This led to key revelations emerging about Konoha's sinister past, inspiring Sasuke to power up for the Kaguya war to come later on. However, it did take a few weird twists and turns along the way that felt forced, leaving it significantly short of what 86-Eighty-Six's similar brotherhood arc accomplishes.
Now, this isn't to knock what Itachi did for his younger brother, but it was a convoluted plan with many holes. He killed his clan for conspiring to throw a coup, left Sasuke and went off, all to make his brother stronger. That wasn't smart as it drove Sasuke into the hands of Orochimaru and could have made him a weapon for the Akatsuki.
Sasuke could also have been killed had Naruto lost patience, so it took too many convenient moving parts. To top it off, Itachi could have harmed Sasuke in battle, not to mention the likes of Kabuto got to experiment on Sasuke, so it was a scatterbrained plan that made him a victim and ended up being done for shock value. Simply put, Itachi was no hero and caused epic destruction, which his brother also followed as he lost the concept of family. In fact, it led to Sasuke then trying to backstab Naruto after they killed Kaguya, just to take over Konoha. Had Itachi just stayed or come home and shown the kid some light, that would have made sense.
In 86-Eighty-Six, though, it's more nuanced with Shin and Rei as they're destined to fight like the Uchihas. Rei lost it when his parents died, blaming his kid brother, and as Rei fought against the Legion, he would die and be turned into a ground-crawling robot himself. Still, his essence kept calling out to Shin, wanting to murder him so Shin's brain could be incorporated into a robot as well. This way they'd get paradise together, a permanent afterlife, and in Rei's eyes, they'd be stronger.
They could then work together to end tyranny and oppression, targeting the racist Republic of San Magnolia. This is what Itachi should have done with Sasuke if he wanted to Konoha straight -- educate to form an alliance together. Instead, he turned his brother against a nation that was entering a heroic phase and trying to undo its nasty past, bouncing Sasuke from villain to villain with no agency.
With Rei, we understand his intentions as they're not cloaked in secrecy. Shin is equally direct, wanting to destroy the robot to free his corrupted brother. It wasn't about revenge, but saving Rei's soul as he was once his brother's hero. This remained true until the end in 86-Eighty-Six, whereas Sasuke stopped believing in Itachi as his idol, which took away from their connection with Naruto's unnecessary misdirection. It felt too inconsistent and topsy-turvy as opposed to Shin and Rei, whose story proves that simpler is often better.