You realize for an Admiral to be seen equal to a Yonkou in this hero driven fandom (where marines are the opposition group and the SHs are grouped with pirates), he has be twice as impressive as the Yonkou,
the real question is you realize this manga is about pirates and freedom and dreams which go back to pirates be the biggest representation of that? that is why luffy believes the pirate king is the person with most freedom.
the marine is the opposition from that they are order and oppression. oda will never make the top brass of marine stronger than the highest level pirates. even yonkou like big mom and kaido lost their adventurous spirit and became symbols of old order are still at heart the highest level of pirate world .
this is not the fandom it is understanding how the manga works.
what you expect is the equivalent of thinking the strongest people in naruto will be those without dreams