Kaido didn't show anything until we got to Wano fights, but we do know for a fact he was stronger than everyone because the author decided to give him the WSC title. If the writer calls him WSS, then he makes him one because that's what his intentions are with the character. He'll show the appropriate feats when the time comes. We, as readers, can't do anything besides wait for more feats. You can't go around making definite conclusions when only one side has feats. That's like saying Katakuri's stronger than Rocks because the former has more feats. We know how dumb that argument is.
He doesn't have to do shit not because his fanboys say. It's because the author calls him the WSS, which encompasses the likes of Shanks and Fujitora, which, in turn, automatically puts Mihawk over them.