I found Fishman Island to be a fucking slog. Punk Hazard started out alright and had interesting things (and it's -along with FI, I guess- the genesis of plenty of stuff that's very relevant right now), but it wasn't too great. Dressrosa was, again, a slog for a week-to-week readthrough, but some of the events were genuinely exciting, it had really good flashbacks and, of course, one of the best villains in a manga filled with great ones.
It's only with Zou, Whole Cake Island, the Reverie and, right now, Wano, where, imo, the manga not only recovered, but is actually living one of its best moments: Zou was fast, relatively unique and so much fun; WCI, while certainly not perfect (it had a very delayed climax that, had it come faster, could have been better), was a ride; and the Reverie miniarc was straight up dropping bombs in every chapter.
So far, Wano has been really fast-paced (few chapters aside), with some interesting twists, gorgeous art and huge stakes. So yeah, it took a while, but I think it's one of the most exciting times to be a OP fan tbh. The future is bright.
PS: the post-timeskip designs are undoubtedly worse imo. The only actual improvement is Ussop (Luffy, Zoro and Sanji look genuinely good, but I still prefer their older looks), whereas some characters (Franky, as much as it fits him) really got their shit fucked up.
But that's mostly me fixating on the first redesign iterations: maybe it's me getting used to their overall redesigns, but with new clothes and hairstyles they look great (like Nami having less revealing clothes and her hair tied up, Franky having more outrageous hairstyles...).
