1) Sasuke literally did not notice Boruto until that blade was in his eye, look at the screen cap he is completely surprised.

2) Otsutsuki can hide their Chakra, we have seen this multiple times in canon. Sasuke would not have even sensed him.

3) They literally just finished a fight with an Otsutsuki, Sasuke does not have Susanoo levels of strength or chakra left especially after being made a pin cushion.

4) after blowing each others arms off they both lost the gifts Hagoromo gave them, which is why you don't see Naruto healing people constantly in Boruto and Sasuke never uses any Rinne powers outside of the switch and asteroid.

5) Just because you can see an attack with your Sharingan does not mean you can react to it fast enough.

6) Yes they have to power down Naruto and Sasuke, because if they made Boruto and Kawaki insanely more powerful than either of their predecessors it would be unbelievable and the same people who are mad about the power down would be bitching that Boruto and Kawaki are too powerful.

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Sasuke losing his eye makes sense, it happened, same way it happened when he fought Killer Bee and got his shit kicked in even with Amaterasu and MGS, just because you can see the attack doesn't mean you can dodge it especially when you just got out of your porcupine cosplay.