I think it's disappointing that such a great manga is so fatally flawed when it comes to females. There's a reason that it's difficult for girls to get interested in One Piece; all of the women are either bombshells or grotesque. This isn't realistic and really caters only to a male understanding of females. Nami and Robin are supermodels who have a very cliched role in the series. They're either nonplussed by the boys' silliness, damsels in distress, or straight-up eye candy. The other women are either monsters or unimportant side characters. The story is told through male eyes and there's not a ton for most girls to look for each week. That's not even addressing the "character designs" which are generally: head, enormous chest, no waist, enormous hips, long legs. All of the relatable women in the series have this body type...the rest are monsters or Lola (who's the butt of constant jokes).
As a guy, I love One Piece. But I completely understand why many girls wouldn't see a reason to read it.