Why One Piece is losing popularity

 I've been keeping an eye on the manga sales now for a fair few years and been making a general note of it. The sales pretty much exploded with the Whitebeard War arc, the popularity of the Strong World movie and then the Time Skip but it's been declining almost continually for a while now.

So all these sales are the total sales after the fifth week the volume was on sale.

Vol 52 - 1.59 million
Vol 55 - 1.69 million
Vol 60 - 2.59 million
Vol 65 - 2.89 million
Vol 70 - 2.71 million
Vol 75 - 2.56 million
Vol 80 - 2.70 million
Vol 85 - 2.40 million
Vol 90 - 1.95 million
Vol 95 - 1.72 million
Vol 96 - 1.63 million

As it stands, Vol 96 is actually the lowest selling volume since Vol 52 which was 12 years ago. Digital sales need to be taken into account and they are very slowly increasing over time but apparently still make up a small fraction of the overall sales.

Even though it's gone down over time, there was a uptick during the final battle with Luffy and Doflamingo but then as soon as that arc ended there was a very sudden drop. It then slowly declined again until there was another drop with this Wano arc but now instead of declining slowly it's actually dropping quite quickly.

Each volume has sold 100,000 copies less after the same amount of time now since Vol 92. So maybe people aren't liking the current arc at all.