Oh my God. Lol. Bro. Kids entire crew got demolished and enslaved. His best friend was forced to eat a smile all because he was weak. And guess what? Even after Oda made these plot points he had Luffy 1 v 1 Kaido and half heartedly gave Kid to Big Mom.
Ida just be doing shit that doesn't come back and influence the plot. He's only gonna let the MC shine. That's just the way it is.
Zoro is not Kid, who is a side character. Zoro is one of the main characters of One Piece. Zoro has outshined Luffy before.
Remember what happened in Thiller Bark when Luffy defeated Gecko with the help of the Straw Hats and the temporary shadow power he received. After that fight Kuma arrived and Zoro saved everyone from him. Zoro not Luffy. Zoro out performed Luffy in the end.
Oda giving Luffy his 1v1 battle with Kaido doesn't stop Oda from having Zoro return and fight Kaido in his only 1v1.
When Kaido was introduced Oda told us he lost 7 times as a pirate.
He's the only Yonko we know the number times he's lost. The reason for that is to let us know losing doesn't mean anything to because it won't stop him from continuing to move on and move forward.
All of that means, Kaido can fight Luffy and finally lose to Luffy and return to continue fighting. Kaido won't stop until he's killed.