Based off what feats? Kagutsuchi has shown greater capabilities of slicing, than piercing. Zetsu wasn't pierced, even being forced through a wall. The concern on Sasuke's face upon being attacked wasn't for s&g, and it sure wasn't the look of confidence that his attack was going to succeed or not. if Kagutsuchi was more effective at piercing, Sasuke would've have favored that over chidori long ago. I have touched the subject with you about Ay's durability, even If kagutsuchi pierced him, it would not have stopped the momentum of his kick, and what damage it would have done. His leg would have simply been punctured through, but still coming down.