The "Big Mom stalemated Kaido for 3 days so she is his near equal" argument cannot be debunked harder than comparing Misery in all it's glory with Flame Torch. One was clashing with an Island sized, CoC infused Gear 4 compression Punch while the other was sliced apart by Law without his Devil Fruit.
Couple that with Kaidou calling Big Mom an invalid & telling Luffy openly that there hasn't been someone who's pushed him this far when he goes Drunken Mode... that does it for me.