He got his title from the world hyping him up for having skill that surpassed even Shanks at the time. But:
- Mihawk has never fought Roger or Rocks.
- Mihawk has never fought Oden.
- Mihawk has never fought IMU.
- Mihawk had never fought Vista. Vista's skill was so formidable when he actually did, that Mihawk postponed the fight. Mihawk saw him as a worthy adversary.
-Mihawk
stopped fighting Shanks. Shanks went on to become an Emperor of the Sea some years after that, defeat Loki and rival his peers. Even the
World's Strongest Man. His Haki was being compared to JoyBoy not too long ago. Not even Shanks remained stagnant enough for Mihawk's title to apply to him.
The story itself is evidence that his title doesn't apply universally. Yet you continue to do so and only for Mihawk apparently? Because the fanbase is not putting WB above everybody in the verse due to his title.