When you said it yourself if your headcanon ZKK do not happen then it's terrible writing, but you yourself do not look on other aspects as well that ZKK itself is really make no sense for the story..
I challenge you to find a way to end the arc and Kaido's narrative arc without Zoro killing him.
I always ask this to anti-ZKK people but they can never come up with a credible way to end it.
-"bombs will kill kaido" => failed
-"bigmom will betray and kill kaido" => failed
-"cp0 will kill defeated kaido" => failed
-"kaido will drown in the sea" => failed
"kaido will be thrown into mount fuji" => failed