The implication is that the offense-based fighters are better than defense-based fights in offense, not that defense-based fighters have a bad offense in general. Certain abilities could rival CoC attacks. Like, Kaido, for example, ultimately used fire to strengthen his offense.
That's literally my argument. Shanks has something better than them that makes him fight better and compensates for the lack of defensive capabilities that Kaido and Big Mom have. GB's life-sucking abilities and the fact that he took far less time to deal with Yamato and others while it took Kaido several minutes to subdue Yamato alone proves he's offensively better than Kaido. That's not gonna chance the fact that Kaido is stronger than GB though.