To the people who are tired of this topic, I sympathize. I am too. However, every time it is brought up, there are an ongoing series of posts that try to ignore it, downplay it, or dismiss it. If it were simply acknowledged as the fault it is, I'd be content with that and move on, but when people try to rationalize why it's okay, that's not acceptable for me to ignore.
Now we have the demographics schpeel. You know, one of the biggest lies propagated by a culture of sexism is that boys and girls' interest are defined by certain things. Boys can't like romance or girls can't like fights. If there is any truth to the matter, it's never been established by actual research, or atleast none that I've ever seen, and it's just presumed to be so as marketers were thinking up what could possibly be popular. I'm of the viewpoint that while there are things that teenage boys and girls might expect to like or not like based on shallow premises, once read, people like whatever is there based on quality. If shonen published a story of a middle aged mother that otherwise had all the marks of a typical adventure story and was well written, teenage boys would love that shit. Because stories are ultimately about empathizing with other people, and since mothers are people, assuming it was well written, there is no reason to think why they wouldn't be all over it.
So the argument that teenage boys can only like OP if it depicts women the way it does is nonsense to me. In fact, more than nonsense, it's an outright reason to depict them otherwise. Oda said that he sexualizes women to the extent that he does because he aims at teenage boys, which when you think about it, is one of the more vile things he's said. He's admitted to intentionally propagating the image that women are meant to be sexual objects for boys. His audience being teenage boys is only more reason to NOT sexualize every female the way he does and to have them be as represented as men, since that is a better way of influencing boys instead of feeding their hormonal desires.
What my point was is that One Piece is a story written for young boys, in a magazine for young boys, so of course the guys are going to have more fights. Just like how in those stories aimed at girls I mentioned are going to have everything revolve around their female leads. The fact that Nami and Robin are as important to the story as they are is pretty progressive and shouldn't be so readily ignored--which it often is in these conversations.
I feel that it may be that way with Robin, but I wouldn't say so with Nami. I feel we never really see her working on maps or anything, and it's just sort of in the background. They established that ships need a navigator, but that was so long ago and Nami has been in there mainly for the wackiness ever since and not much else. Imagine if they there was some plot device that would have killed the strawhat crew unless they had a cat on board their ship. If they got a cat early on and it's since then just been chilling in the background, then I'd argue that the cat would be a decorative piece, even if it's narrative purpose is clearly established as vital to the crews survival. That's sort of how I feel about Nami. It's not like we ever see her really working on maps or navigating. In fact, the last time we saw something like that, it was when they were deciding on where to go after Fishman Island, and Nami wanted to go to one of two safer places, and Luffy ignored her and "F that, lets go the most dangerous Punk Hazard", basically ignoring is navigator. Not to mention they get caught up in the random events of the sea regardless, and Nami doesn't seem to do anything about those. They just sort of ride it out until it's over. The last time I remember her actually influencing the plot was back in Hazard Punk where she made it a point to defend the kids while the other strawhats didn't really care all that much, but it was a very minor point and I don't remember her making any other kinds of assertions for a long time before then.
Robin I'd only partially agree with, since her interest is in the whole void century thing and all, but the void century is a very minor aspect of the strawhats ongoing story so far. I feel like the only thing distinguishing Robin is that her interests are worldly, while every other character mostly has their interests oriented around themselves, and the Void history and the ancient weapons are part of the world building. However, 95% of arcs are not about that. I've been open about the fact that Oda does a better job than Kishimoto and such because he does give the female strawhats their own meaningful backstory, but that only goes so far as far as the overall story goes.