Blame the anime "cameraman" for making the female heroes look like they are just fanservice... I mean... you see a female character talking and the "cameraman" aims either on their chest or legs... Either he is really, really short or he needs to find a GF....
To be fair, until we learn what the one piece stands for, we can't really judge Oda for focusing on Luffy a bit more. There are good theories and even hints in the manga that point to Luffy actually being the One Piece which would actually make One Piece a story about Luffy.
When it comes to the crew, the only ones I am not happy with is Nami, Ussop and Sanji.
After their 2 year break, Nami's only power up was Zeus and the Clima tact that Ussop made for here. If you think about it, all her weapons are the technology she took from the sky-island. Other than her weather knowledge, she hasn't achieved anything important herself and she has been stagnant for a long time. An excuse would be that this fits Nami's character as a thief. She manipulated the scientists to get their technology, she stole Zeus and also stole the clima tact, but I still find that her character development is lacking.
Ussop... Other than his amazing shot in dressrosa, the brave warrior of the sea has been running away from the enemies again and again. Very disappointing... I still have hope for the Elbaf Arc being Ussop's development Arc.
Finally Sanji... I haven't seen a character being mistreated more than him.... The absolutely only reason I don't see Sanji the same as Zoro is because Oda has been making him look like a fool and a pervert almost all the time... I am fine with the occasional gag but he overdid it with Sanji to the point that it's not even funny anymore. Sanji has his glorious moments in each Arc, I am not gonna lie, but they are overshadowed by the constant harassment.
Other than those three I am happy with the rest!
Robin's development is insane! Learning Fishman Karate and awakening her fruit plus she is extremely important because she is the key to the ancient history. If the "Cameraman" remembers that he is not shooting porn from time to time I would have had 0 complains with Robin's treatment!
What can I say about Zoro... If the anime was called Zoro I would find it logical at this point! His feats since the beginning of One Piece are breathtaking. To tell you the truth, no matter how much I like Luffy, Zoro will always be a step above in terms of his development because you actually see him training none stop to become the strongest. I ve only seen Luffy train during the 2 year skip and in Wano.
Brook and Jimbe were amazing during the Cake island arc and they are still going strong and Chopper... Well he is the little kid but still developed a lot as a character the past few arcs.
In the end of the day, this is a series about Luffy achieving his dream and becoming the King of Pirates, I mean we ve been hearing this from episode 1, so it's only logical to focus a bit more on him, especially now that we learnt that he is connected to a very important figure of the past.
One thing is for sure though. Even after gear 5, Luffy made it clear that he wasn't worried about anything happening below (during his fight with Kaido) because he knew his crew were dealing with it. I don't think Luffy's crew will ever become less important than it is unless Luffy becomes so strong that can defeat an emperor's whole army on his own.