I mean tbh, what more could Zoro have done?
ZKK couldn't have happened because defeating Kaido was always Luffy's role. Luffy always beats the main villain.
Zoro also couldn't have led the samurai, as that was Momo and Kinemon's role, and regardless of Zoro's ancestry, his is an outsider in wano.
I think Zoro did exactly what his character was always set up to do. He saved Luffy on the roof multiple times. He saved him when Luffy's haki ran out, then again when he re-directed hakai, and then one final time when he used asura to prevent kaido from killing Luffy in 1010. He also took out Kaido's right hand man, helping Luffy beat the beast pirates.
Ultimately, I think ZKKers have a misconception about Zoro's character. They don't realize that Zoro's role was never to steal the spotlight from Luffy, but rather to help Luffy achieve his goals. ZKK was basically a fantasy where Zoro usurped Luffy as the MC and stole the show by defeating the main villain, which is why so many people heavily opposed it. Similar to how Sanji fans sometimes try to push sanji into Zoro's role, Zoro fans basically did the same thing to Luffy with ZKK.