Boundman has literally shown the best attack power among all high tiers, a Kong Gun was overwhelming Cracker in a direct clash and had even enough power left to destroy his soldier. A simple Kong Gun made Big Mom use haki and her arm was still rattled, basic G4 moves as Kong Gun and Rhino Schneider bypassed even Katakuri's superior haki- defense and send him flying:
Yet even a Kong Organ wasn't strong enough to get to Cracker's main body:
Even when the biscuits have been softened Luffy admitted destroying them is pointless,
simply cause they reassemble too fast...
Cracker had simply a infinite wall at this disposal, perfect suited for one dimensional brawlers as Luffy, the biscuits being hard countered by Nami's rain, but Luffy still not being able to bypass them r simply proves that even further...
I personally wouldn't insist on that since there have been other factors regarding the plot, you have to take into considering , but heck if you take Luffyy's statement at face value, then KKG was useless as well.
Law would get easly past the soldiers, yet Luffy couldn't even with them being hard countered and Luffy having access to Boundman...
You could make a case for Sabo, Kuma, Magellan, Ace, Mingo, Morely, even med tiers as Perospero, or Pica that they would have better abilitys to deal with the soldiers. Are they all stronger than Luffy?