@Jabra:
Apart from all that, One Piece simply became less appealing for certain parts of the fanbase.
Those who considered One Piece to be a somewhat progressive Manga were turned off by all the weird stuff Oda pulled since the timeskip, while the faction who loved the typical battle choreographies (Straw Hats vs. enemy crew of the arc) had to get used to fights being off-paneled left and right and the spotlight given to sidecharacters.
I remember the time around the Chapter 755 (Man's World) to be the most severe example of that. It felt like dozens of people got banned, while many older members turned away in disgust and/or boredom.
While it's fair to say Oda is not especially good at handling his female characters and never has been, the manga's hard anti-imperialist, open-borders political stance and good faith (if flawed) attempts to include queer characters are consistent on both sides of the timeskip. My understanding as that the series' philosophy as a whole falls at least a small way to the left of Japan's dominantly conservative culture. That hasn't changed one bit over the years, even if it comes across as less of a contrast to the dominant narrative from a western perspective. Chapter 755 is my personal least favourite chapter, and I'm sure I'm not alone in that, but it's the same crap we always had from Sanji before the timeskip. I roll my eyes and tolerate it, same as I did with Sanji's Kalifa debacle.
I think any change in readership/user numbers here is mostly the fault of centralised discussion forums like Reddit, with, of course, something to be said for the high barrier of entry set by the series' length.
