Kaido's reign in Wano means a lot of things
Even entering Wano is already known as a hard task. When you include Kaido's huge army of SMILE users, all of his available weaponry (the one that was used to defeat Big Mom for example) and his crewmates, everything fits.
Luffy himself stated he couldn't understimate the territory he was in after he got overwhelmed by Ulti. He needed to find another way to reach the rooftop cuz he couldn't pass throug King and Queen
King lowkey stopping the Big Mom Pirates from reaching Wano is already a big deal
Admirals are solo fighters for the most part. Meanwhile, an Emperor's success is completely tied to their crews, their territories and their infamy