It was extremely impactful, but you're right. It didn't look impactful narratively, and that's because Zoro isn't done with Kaido. If Zoro's Asura looked impactful/with finality, then readers would think Oda is going overboard with Zoro when he does do ZKK.
But because it didn't, Zoro narratively has to have closure with Kaido, thus prompting ZKK.:cheers: