Yes you're absolutely correct, Shanks could be stronger than Mihawk.
However, he's not, because Mihawk has the title of Sekai Saikyo no Kenshi, and Shanks is a Kenshi.
So if your thread was about proving that simply having greater sword skill doesn't make Mihawk stronger than Shanks then good stuff, great thread.
But if your thread is about proving that Mihawk's title no longer holds meaning then that's incorrect. Zoro's dream may be to be the strongest Great Swordsman ever, but that is not Mihawk's title. These are two different topics.
What you've done, however, is prove beyond reasonable doubt that Shanks is indeed a Swordsman. And as a swordsman, he is inevitably included in Mihawk's title which was reiterated multiple times last chapter to be the World's Strongest Swordsman. Not World's Most Skillful Swordsman, not World's Strongest Dai-Kengo, World's Strongest Swordsman period.