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.
Nonsense
- Increase in physical strength , durability , speed.
- ability to fly
- ability to lift entire island which can destroy entire city as stated in manga
- cutting winds , lightning , fire beam , tornadoes
- huge flaming dragon
All this alone makes presence of actual top tier necessary just to stop you in dragon form.
Kaido is Kaido thanks to his devil fruit powers and durability. Oni strength and toughness is a myth nowhere in manga they get any hype, in fact a way superior beings like giants dont have any extraordinary toughness or strength ( they do compared to a fodder true ).
1. Without feats like lifting Onigashima and giant flaming dragon there is nothing that puts Kaido above other top tiers .
2. No Boro breath , no wind cutting , no flight make it Kaido has no long range attack and impossible for Kaido to deal with flying targets .
3. Coc gets stronger with user himself getting stronger and Zoans provide direct power boost to user meaning Kaido coc strength would be lower without his devil fruit.
4. His dragon scales durability is what makes him relevant against other top tiers , take away this and he bleeds from basic kick like against Xebec. Without his dragon durability there isnt single admiral outthere that would have problem putting Kaido down .
Katakuri missed a lot by not having dragon devil fruit.