Ennies lobby was different in that the Strawhats had no strong allies on their side who could combat those strong people. Look at Dressrosa and Punk Hazard for example, where allies actually defeat some of the top antagonists in the arc. This is a war, typically arc outlines may not apply here.
If all of them fight Kaido and Big Mom, who would fight the Tobi Roppo, if Zoro, Sanji, and Jinbei fight the calamities? And then what about the numbers? What if Big Mom’s crew shows up? It’s not that clear cut.
I keep telling ya all that advcoa is not this grand attack power powerup, its armor pen. Doesnt add too much damage to your already preexisting physical power with haki, just allows you to hurt targets you otherwise couldnt.
If you can already hurt targets then there shouldnt be much of a difference between using it or not.