I agree with the spirit
I would prefer Oda to develop existing character rather than creating out of thin air « admiral candidate ».
But to be fair all the vice admirals introduced till Marinfeord were really far too weak to be crediblle possible admirals. Oda would have needed to make them far stronger than before.
About Momonga hype : lot of panel times (even in movies, special episodes etc, cool design and personality, the Hancock moment : retrospectively you can see that some powerful guys can be turned into stone easily so Momonga resisting like that was a nice feat. Momonga was also promoted to be the chief and governor of the former Marineford, the second biggest Marine base in the world.
So out of the other VA the man stands out a little bit