Yeah this is just some piss poor Admiral 50 years ago
The navy evolved with Sengoku and Garp (honorary) being Admirals who rival Roger
Now there's Akainu 5bil
Kizaru the owner of Nika
And Kuzan the fist
Some scrub from 50 years ago isn't changing the facts we know about the current generation or even Sengoku and Garp
So all this time, Big Mom was referred to have potential like the admirals 50 - 60 years ago. Means her potential was like that nameless admiral.
Now with the mid and current era, the navy got stronger than ever before. I guess, if Fujitora or Greenbull didn't appear, they would have to take in the admiral candidates such as Gion and Tokikake. They were strong enough to be considered candidates but they got quickly outclassed by two newbie navy soldiers who moved up into the career ladder as admirals. That's why it was mentioned how the navy got stronger and why Doflamingo hyped Fujitora and Greenbull like that.
I really can't wait to see their biggest accomplishments and how strong they truly are.