The people from WG and especially OP readers suffer from memory loss, and for them, nothing is ever enough—if a statement isn’t repeated countless times, it isn’t considered valid.
We already knew that Kaidou was feared simply for existing—this is stated in Ace's novel.
After that, we have Doflamingo and Big Mom elevating Kaidou to the heavens, with Big Mom, a top-tier and a Yonko, calling Kaidou
"that thing."
Third, we have Blackbeard literally stating that Kaidou is a terrifying monster. Blackbeard—an Emperor with two Devil Fruits, whom Rayleigh admitted he would lose to in a direct 1v1 fight. The real issue is that deniers always find a way to downplay statements, and they could easily argue that Blackbeard's statement isn’t enough—after all, who’s afraid of Kaidou? Just random nobodies and low-level fighters?
But Oda took it a step further. He showed that it’s the
top tiers who fear Kaidou. People thought they weren’t included, but Green Bull literally confirmed that
he and the others fear Kaidou, with Kin’emon reiterating the same thing.
And now, Gaban—the number two of Roger...
And this is not new, kaidou was already feared 20 years ago and Oden himself stated this.
The gorosei were afraid of tasting Kaidou's wrath.
And we have Whitebeard who never dared to go to Wano, stating that there would be too many casualties between a fight against Kaidou and his pirates.
Let me say this: it’s not just Shanks, Blackbeard, Prime Whitebeard, Oden, Gaban, Green Bull, and the Admirals.
Blackbeard? No—EVERYONE fears Kaidou in this manga.
It's like
@nik87 said, every old and intermediate generation is nothing more than hype tools of kaidou.