First off, databooks shouldn't be used for powerscaling. They're extremely inconsistent, contradictory, and full of hyperbole. So right out of the gate your argument is invalid. However, I'll still humor the point

>with a power to change every one of it's properties, allowing it to alter it's attributes in accordance with the attributes of the attack, rendering the attack ineffective"

This doesn't explain how it actually works. It can just be anti-gravity? We would also assume that a shield needs to be hit by an attack, and you can't just be hit by gravity. It's always effected by gravity. Also this doesn't suggest he can use it offensively 

>a shield that can repel **any** attack

Repel: drive or force (an attack or attacker) back or away

Once again, this doesn't suggest he can use it offensively. Repel is specifically a word used in a defensive context. So he can't just smack a chibaku tensei and negate it