F.e. to deal with King.
In my opinion, it would make more sense to get this grown like that. If they are able to go now for first mates of a Yonko, like King, as double, it is realistic to get them to win solo against a first mate next time. Also with Kid und Luffy. If they get down Kaido now as Team, it is realistic to assume Luffy can beat Big Mom solo on Elbaf.
My thoughts about them getting dragged out is more or less based on the next power level steps. Luffy still needs to get on the level of a Yonko, Zoro needs to get on first mate level. Same for Kid and Killer.
I mean, whats next for Luffy? Elbaf with Big mum (most likely), after that something above, like Blackbeard and then we come to the final war. If Luffy and Zoro now would be above Kaido or respective King, what kind of growing should be then needed for Blackbeard Crew? Or for the world government? There must be next steps.