People forgot that in OP having ridiculous and moments of weakness does not affect your overall power, other top tiers like Garp, WB or Shanks have suffered of it just as well and let's not forget Luffy, who even after becoming the PK will be just as stupid and goofy and will still be beaten every day by Nami.
Plus the fact that Oda used such absurd plot devices to prevent the Straw Hats from being confronted by BM with her real power says that they would have been utterly massacred by her in normal circumstances.