You're joking right? I know you know what it means to be king of something. Do you honestly think that just because Luffy finds the One Piece, that all the Pirates in the World will simply just bow down to him?
All the Top pirates in the World are aiming for the summit, and want to hold that title. They are not going to acknowledge someone they view as beneath them as the King of them all.
Luffy had the same exact mindset pre-skip that all he had to do to become Pirate King was to find One Piece, and that is all that it would take. Never once did he ever mention beating admirals and yonko's to achieve this. So do you really think it's a mere coincidence that after training with Rayleigh (The right hand of the Pirate King) that his mindset shifted to needing to be capable of defeating all these opponents?
If someone like Buggy accidentally found the One Piece, do you honestly see the likes of Kaido, Shanks, Mihawk, Big Mom, Blackbeard, Luffy, and the list goes on and on, acknowledging him as the Pirate King?
And then what after that? One Piece is found, and its purpose in the World will be fulfilled. So there will never be able to be another Pirate King as long as anyone lives because there isn't some treasure for everyone to race to find? The title disappears forever?
And to even further drive how nonsensical the argument is, was there some kind of World meeting held amongst everyone to decide that Roger finding the One Piece, would make him the Pirate King? You know, the treasure that nobody ever knew about. So people just got together and decided that one day someone would find some hypothetical treasure that may or may not exist, and when they do, that will be the day they announce a Pirate King?
And let me guess, all this stuff Oda has been throwing at us to showcase that in order to be the Pirate King, you have to stand at the pinnacle of the Pirate World is just fluff, right?
Kaido and Big Mom deciding they would find the One Piece together, and then fight each other to the death means nothing? In truth, if they reach Laugh Tale together, the one who touches the One Piece first is the REAL Pirate King.