His bounty was frozen at half a billion bounty despite being a retard walking around with an old woman.
Compare that to Jinbe, who was at 438 million after Marineford or Luffy and Law who only reached 500 million each as captains when they took down entire country ruled by a Warlord with one of, if not the most powerful non-Yonko crew in the world.
He also was casually negging entire crews allied to Whitebeard, while even YC like Izo got caught and hurt by random Beast Pirate fodders or Kid, Zoro and Killer getting tired from fighting large number of Gifters.
And being compared to young Whitebeard, which never happens with non-YRH YCs (King had durability like Kaido - even higher actually, Zoro's Ashura was compared to Oden - though not actually as impactful and Katakuri's CoO is only surpassed by Shanks in how far it can see) certainly leads credence to him being above most YCs.
He is far closer to Katakuri than he would be Cracker, if not stronger, but who knows.