I dont understand how Women are dumb in one piece when we have Nami and Robin in the main cast. I can agree if you say women are not depicted powerful or competent in one piece but calling them dumb is a big stretch.
Nami ( makes maps and is the best navigator/weatherman )
Robin ( Archeologist )
Yamato ( taught her self how to fight just like Kaidou does and mixes her Devil Fruit with her style )
Big Mom ( conniving and smart, he tricked Judge and almost killed him )
York ( lives the most peaceful life of the Punks and female cast in general, but it's because she has to do the most important yet casual things for Vegapunk and his clones, without her they'd be dead from starvation and lack of sleep )
Black Maria ( baited Sanji and Robin into a trap to murder them )
Women are very useful and smart in One Piece, just gotta look harder.