@Kizuchan:
It's a problem because there are far fewer female characters. Post-TS it's Shirahoshi, Otohime, Koala, Monet, Tashigi, Sugar, Violet, Rebecca, Nami, Robin, Mansherry, Baby 5 for more "major" roles. That's 12 female characters with any kind of notable presence. Compared to all the male characters? Very, very little and with these few characters there are these predictable patterns. Girl fights, support roles, princesses with similar personality traits, defeat and humiliation through emotions, fanservice. It's a much more notable problem. Earlier in the series this wasn't as big of a problem because the few characters that existed were all treated pretty decently. But again, I didn't want to start this again. It might derail the thread.
I'll just address the bolded since [King Cannon] said pretty much what I was gonna say.
@Kizuchan:
Girl fights
I noticed, but that's mainly Nami's role when it comes to major antagonists. I mean think of it this way, in the Blackbeard Pirates, there's only one female, meaning who would Robin fight? Yes, a male. As far as I remember, Sanji is the only one who's had issues fighting women stemming from how he was raised and his chivalry (Kishido) and to an extent, Zoro with his development of bushido but not as cut and dry as Sanji's ("Beast" chapter title). Zoro expressed strong Ki (intention) to cut Monet (how her cheeks bled) and expressed Sakki to traumatize her, Sakki is the intention or the aura to kill. Whether it be Kaku, Monet or any sentient being ill-prepared enough and capable of fearing for their own life, Sakki can mess up your mind, that's what was shown and portrayed as well as Zoro's path development in terms of Bushido and Asura.
Tashigi did indeed get stronger but her opponents have always mostly been males but those that are out of her league, whether it's to show her rash decisions despite being stronger or to emphasize the hardships of being a swordswoman or possibly both, I'll leave that to you to interpret. However, again it's not as cut and dry, when Zoro stepped back and let Tashigi fight Monet, she was still clearly outmatched by the Logia user. I believe Zoro stepping back, followed by giving Tashigi the credit and stating clearly that he's above her is not out of malicious intent but a way to tell her she's still lacking which lead Monet to call him "cold". Tashigi however, had a very sad expression cutting Monet, believing that it was her duty to strike the finishing blow which gave us the ambiguous ending of Zoro stating that he would've cut her if Tashigi didn't. I can agree with the Sugar thing the first time around but the second time, it was a legitimate defeat, it wouldn't have matter what the ammo was. I mean I know Oda showed dead children but I think it'd still be troublesome to show kids actually being abused.
@Kizuchan:
support roles
What's wrong with support? I can think of one guy who clearly took pride in support recently in the arc but let's move on and I presume you only mean after the timeskip, yes? There's Big Mom obviously, Tashigi, Monet (who almost took down half the crew), Jora (who almost took down half the crew), Sugar (she even clearly said it; who would've taken out Luffy and Law herself), Baby 5, and Rebecca. Those are the ones who didn't fall in the support roles, not counting their losses and broken spirit.
@Kizuchan:
princesses with similar personality traits
I understand the pattern here, that I do. I presume you mean crybabies (possibly the pink hair with the exception of Mancherie) who ends up being protected? I acknowledge and agree with that to a certain extent but again, not as cut and dry. Shirahoshi for instance, despite her little knowledge of the outside world and small self-confidence being confined in her room for years took it upon herself to live by her Mother's last wish with keeping the knowledge of the identity of her Mother's killer to herself. She also held off the gigantic ark Noah from falling and killing everybody. Mancherrie's powers, almost seemingly to address the tropes, are her tears. She also clearly stated that was her own way of fighting, despite being a Princess. I've said my piece on Rebecca on the previous post but to state it much clearer, she didn't want to be stronger, when she made her declaration full of tears and her eyes glancing sideways she stated she was sick of being protected and implied that her reason for fighting is to get the Mera Mera to fight and defeat Doflamingo. Rebecca did indeed encounter Doflamingo but was immediately controlled, as Luffy realized back in the Colosseum that she was a pawn and that there are darkness in the country at play (Diamante also even stated they didn't intend to give out the Mera Mera), he took it upon himself and promised Doflamingo's defeat in return for his debt to her - resulting in the ending shot of Luffy resting on her lap drowned in her tears.
@Kizuchan:
defeat and humiliation through emotions
This was part of my argument in my previous post actually and one of the topic in my thread. It's all in the portrayal of Ki and Haki. Specifically, in Rebecca's case as well as the story in general, the Ki in terms of feelings and mood (emotions) are directly tied to their spirit (Ki), which in turn affects their Haki, whether it be passive (in-story) or active. In other words, Rebecca's circumstances always gets in the way of any proper showings of her true ability, except possibly in the encounter with Doflamingo but there's no shame in being controlled by a deranged and experienced demon of a King.
@Kizuchan:
fanservice
Yeah I don't really get this. Being an experienced viewer and reader of such genres - with the exception of the breasts, One Piece fanservice is pretty tame. If you bring up the anime then I can agree with you though…. The only issue would be Rebecca's gladiator gear but it has it's practical use of being lightweight, as well as some possible story explanation of being forced to fight in a humiliating fashion.
Anyway, I apologize for derailing the thread.