The azure fruit wouldn't have made a solid top tier out of Katakuri.
I'd argue that for the most part the mochi fruit even grants stronger techs and attacks.
Oda scaled down the physical strength increase from hybrid transformations down that much, that it would barely give Katakuri anything besides its great durability and the dragon form as it is.
It's a good fruit for someone, who already has a top tier fighting style like aCoA+CoC hakiblasts or CoC infused swordsmanship, but other than that - besides flame dragon torch - it's really not op.
It's essentially just a better dinosaur fruit with a durability threshold that doesn't even bother top tier attacks in the slightest.
Add that a whole lot came from Kaido in the first place: Oni strength and toughness, top tier CoC, TB speed, drunk CoC increase..
Put it on a guy like DR base Luffy or base Kid and you know how strong it is on a normal guy.
Base Kaido himself is just that powerful.