Mmm no. When Kaido said "you couldnt be joyboy either" or neither... he referred at Luffy who lost against him. Only that who defeats him can be Joyboy.
That could be a valid interpretation too, yes.
And even in that case, Kaido somehow came to realize that he is the gatekeeper/harbinger of Joyboy.
When and why did he come to realize it? Oda never showed us. One can also reasonably assume that it could be one of the main reasons why Kaido said "I am here
BECAUSE it's Wano"
This is what I am talking about.
Oda sprinkled many panels here and there hinting/teasing of a much greater character in Kaido, than what we got to see on screen. We can only
assume, Oda didn't deliver. Hence the disappointment.
He had potential to be much more, was teased/hinted of being much more. Yet Oda failed to deliver on that. No character defining moment, and no backstory (the 5 panels don't count lmao), nothing.
This simply isn't how you deliver a character who has defined the
ENTIRE post TS, Kaido defined almost
500 chapters and this is what we get from Oda. WTF???