Luffy hasn’t been officially declared a Yonko yet because the title of Yonko is reserved for the four most powerful pirates in the One Piece world. Even though Luffy has incredible strength and has defeated powerful Yonko like Kaido and Big Mom, he hasn’t been officially recognized as one of the four most powerful pirates yet.
However after his victories, Luffy is often referred to as the ‘Fifth Emperor’ due to his immense power and influence. It’s likely that he will be officially recognized as a Yonko in the future, especially as he continues to grow stronger and gain more recognition in the world of One Piece.
So, while Luffy hasn’t been given the official title of Yonko yet, but his actions and strength have already put him on the same level as the Yonko.
