"Your mind and body are finally able to harness the potential of your ability!"
Kizaru's Fruit is light, which is fast. But, as we see from Saturn, Kizaru's work has been "slow", and he's been conflicted this entire arc.
Kizaru's Unclear Justice IS his justice because his mind and body aren't on the same wavelength. We saw him close his eyes while trying to shoot Bonney/Vegapunk.
Kizaru's Justice has to become Clear for him to be able to Awaken, which makes sense, because light itself is all around us, but appears clear to our eyes, rather than blinding.
This was Kaido's core issue, too, IMO: Kaido wanted to be Joy Boy, and couldn't Awaken his Fruit because he gave up on that dream, so his mind/Will could never keep up with the sheer power of his body + Fruit.
Kizaru has to reject being a corporate slave and reclassify his justice before he can Awaken his Fruit, IMO.