@icel:
legit curious about this and the effect it has on merch, i actually took an extended break from reading the manga around a year and a half ago after getting frustrated with it (still waiting for it to pick up again…) so i've been completely out of the loop - but do you mean OP's popularity has gone down? a lot of people i know got fed up with it and dropped it too, and after virtually years of it getting praised as practically flawless i've noticed an increasing turn towards open criticism... but i figured that was mainly outside of japan, and that its still just as popular as ever there?
As much as I love One Piece I do feel it's took a nose dive over the past few years. Aside from Luffy and one or two others the development of the main crew has been pretty much non-existent. And this has been the problem since the Time-Skip. Robin, Chopper, Nami and Brook haven't really had a chance to shine at all since before the Time-Skip (and even then we are looking back at Enies Lobby and Thriller Bark times.)
Its not just that however. There are a ton of problems. I can only speak for what it's like in the UK however I go to a lot of conventions and know a lot of stall/shop holders and there's a lot of issues with the past few years that is stopping One Piece and it flourishing. The main one for a lot of new people is the series is just too long. People see 800 chapters, 700 episodes and instantly quit. Compare that to a series with 13 episodes where you can watch most of it if you have an hour or two spare. Granted the ones who do get into it love it and binge it. But to a LOT of people it's just too long. Which is an impossible problem to have. The other issue is that a lot of the characters being focused on don't appear until 500 episodes in. I know people who cosplay Law but are only onto Drum
Added to that the series is just not accessible to a lot of people. The only way to get it over here is to buy the DVDs, which at £25 each and there's already 12, which doesn't even complete Enies Lobby yet it's £300 just to get up to date. Other currrent popular series like Soul Eater, Black Butler, Blue Excorcist, Fairy Tail, Attack on Titan and the like are all on Netflix. Which most people already have. One Piece is not. One Piece isn't even on Crunchyroll over here. So two of the current major ways to watch the series we can't. Its either buy expensive DVDs or Illegally torrent it.
The other issue is what Merch we are getting. It's appealing to little more than fanservice. Or its the same characters over and over again. My local anime store has completely cut back on buying in One Piece merch because everyone who wanted Law or Zoro got them, and they just aren't buying multiples of the same character anymore. The lines just aren't varied enough to keep people buying. My local store has actually went to the point of trying to source older sets which include the likes of Chopper, Usopp, Robin, Brook, Franky, Hancock etc because they actually want to have those on the shelves as people do want them. (and not in a fanservicey version.) Thats not saying the other characters don't sell at all. But when it's almost impossible for stores to stock the main characters some are just choosing to wait until they sold the ones they do have. This is just the issue I've seen with the ones local to me and ones at conventions but I can only imagine it's similar elsewhere
But this is just one of the issues with merch, the other is that A lot of the lines (Figuarts, Grand Line Men/Ladies/Children, Chibi-Arts, Styling. S.h Figuarts and most of the smaller lines) are dead or releasing once in a blue moon. One Piece just isn't putting out figures like it used to anymore. Even if we are getting new lines we are getting a handful and then they're stopping. Other lines such as WCF and Scultures have reduced what they're putting out. Megahouse puts out one every other month I think now? The Funko line announced a whopping four variations for its initial line and is being met with middling responses (some love, some hate, some are confused why there's no Nami, Zoro etc)
I actually looked at what I've bought One Piece wise in the last 12 months. I've spent less on that than I would have 4 or 5 years ago. It's sad. My money seems to be going to Goodsmile for Nendoroids or Nintendo for Amiibo instead.