I just watched a Wanokuni episode, and it is the first One Piece anime I have watched in a long time. At some point, I lost interest in the waning quality and over use of still frames, and dragging out scenes. I have to say, this looks amazing! The art looks much crisper and more colorful, and there seemed to be less "time-waste". What's changed in the last few years?
Well, for Wano?
We got new series directors, one of which is known for "modernizing" the long running shows he becomes series director for(ala DBS during the tournament of power arc and DBS Broly). The head series director, Tatsuya Nagamine who did all this, was also the director for film Z. The biggest notable change under them is the change in composite(we also changed photography departments, with the implementation of a line filter, which gives the lines some nice variation and thickness, and the new photography department has also emphasized the use of gradients in shading and has generally resulted in a warmer colour palette for Wano.
The other two series directors are experience episode directors in their own right, with them being responsible for some of the biggest episodes of the anime.
We got a new character designer this arc as well, which is noteworthy because we haven't had a new character designer in 10 years(the new character designer is Midori Matsuda). The character designer is also serving as a chief animation director beside the one we got in WCI, Keiichi Ichikawa, meaning that both of them tend to handle the important close up shots to provide a level of visual consistency between episodes of the show. They also tidy up the artwork of certain animation supervisors for consistencies sake.
In other words, a lot of shit.