But none of them have proper navigational skills to sail on the absurdity that is the Grandline's weather conditions.
We're not factoring that in this scenario. If they clear one place by defeating the enemy/enemies present, they move to the next. This is the Konoha 11 with all their current abilities travelling the same Grandline path the Strawhats did.
Also, they don't run into Mihawk or Aokiji lol. It would end too quickly.