The next time we see Katakuri he's going to use advance coc.In order to use each type of haki at the highest level, it is necessary to be one of the strongest.Ray's decency that there are people who can see the future among the strongest is a proof of this.
Even the Dof will do it the next time we see it.
The level of coc is important.It is not so difficult to add to the attacks.Yamato could add it, but she can't splitting the sky.Luffy, on the other hand, did it only in its base form.
That is like say Sabo will fight Blackbeard or zoro would not fight kadio.
Claiming luffy won’t fight Akainu is like claiming luffy won‘t fight Blackbeard.
I can say sanji will fight IM guy or sabo will fight IM by your logic.
That's endurance, not durability. Receiving damage part is the only thing related to durability. If you receive damage to begin with, you're not as durable as one who doesn't from similar or better attack.
No shit Kaido has far better endurance than King. At least until King starts taking serious damage and keep going.