This is some stupid ass logic. Because Mihawk has a sword, he can't lose in any other way outside of the sword is what you are saying.
Roger can't use his overwhelming Haki. Shanks can't either. Whitebeard can't either, nor his earthquake powers.
Again, one line this chapter is harming your cope argument. Kaido is talking about Roger's haki to conqueror the world, not a DF power, and certainly not swordsmanship