Momo is fucking an 8 year old (aged 20 years) with no haki you crayon eating moron
Even with ryou you can only do shallow damage to kaido
No amount of the thematic nonsense Is in place for momo to even tickle kaido with a sword
So all the arguments you can make are based on powerscaling which Oda has been fucking left and right during the whole series like Crocodile clashing with so many characters in Marineford, giving Luffy the biggest asspull in the series after 2 consecutive powerups in the same arc or having Big Mom use ACoC only for fodderizing Page One. You are reading what you want to read and ignoring all the rest of subtext and implications.
Haki literally means ambition. The way of the swordmanship, as shown many times in One Piece, is being able to cut the things you want to cut. If Momo shows enough ambition to kill Kaido, Oda will decide that Momo kills Kaido, even if he's 50000 times weaker than him.
I'm seriously glad that some ZKK supporters are actual reasonable people that you can argue with because if they were all like you jesus fucking christ what a shitshow.