why do you think that way?
Him being an admiral allows him to be involved in stuff all around the world. If he was the Wano Shogun, it would be hard to build up storylines like his conflicts with "evil marines" like Aramaki and Sakazuki, and a Wano Shogun Issho couldn't be responsible for eliminating the Warlords as an organization.
I don't see how him being an admiral is worse for his character than being Shogun, though Momo is pretty awful and should have been replaced.
Anyway, I like the World Draft. It makes the OP world feel bigger as a whole, there really are just top tiers like Issho and Aramaki hanging around that aren't affiliated with an I just hope he introduces more marines as being drafted from it.