That's what I thought too, Law DF turns really useful for this.
But even if Law shambles her at the entrance of Onigashima (or any point on the island) that would just delay her return, I don't see a possible way to actually remove her tbh
by far kaido's biggest damage output is when hes in dragon form lol. hes just also slow and a gigantic target for a group of people to hit him so he went for speed blitzes in human form and now is going hybrid for speed + power. but the power is zoan form. always has been
It's not over, they just fought in the time it took for Luffy to recover it seems. Theyve been able to dodge the Yonko's attacks. Again, we still have no idea how serious either Yonko is right now so there's that.
I reckon too they had squabbles.. i deduced that the plot in the dome was progressed in 10+ minutes, in those 10 minutes luffy was back to his form... after stalling kaido and BM, and they clashed a bit...after that.. hence why Kid suggested what he did...
but its crazy to assume that hybrid kaido couldn't chase em down in his hybrid form..