Excluding this final saga, if I had to rank the Post Timeskip sagas from worst to best:
4. The Dressrosa Saga. Yes, I dislike this even more than the Fishman Island Arc. While Doflamingo was an excellent villain and a beast of an opponent, the pacing of the arc was atrocious, all the female characters got next to no real fight time (which while always a minor issue wasn't nearly as bad before the timeskip or in any of the other Post-TS arcs) and were mainly used as plot devices, it contributed the least to the lore compared to other post-TS arcs IMO, and was often rather confusing to follow due to a massive mishmash of events and characters poorly handled all at once. Of course, I know it was the first real arc after the timeskip and Oda was trying to experiment and see how he wanted to write the story, so I won't give him too much crap. The Punk Hazard Arc was fine, though.
The positives were Doflamingo (as already mentioned), Law, the creation of the Grand Fleet, the World Government being humiliated by Issho (leading to the removal of the Warlord System), and the Punk Hazard Arc as a whole being fun and having a villain who the Straw Hats couldn't defeat with just their superior power. Also, Law as a whole.
3. Fish-man Island Saga. In contrast to Dressrosa, this saga had the worst villain in Hody Jones (seriously, they show him growing up in a dirt-poor district while the Fishmen Government gave the WG a lot of money and support, you could've at least used that to make Hody sympathetic, Oda). However, aside from the happy feelings of seeing the Straw Hats together again, it was cool to see them use their new powers (even if the fights were all too one-sided), some nice mermaid fanservice that didn't go too overboard for the most part, some nice lore, and Jimbei getting proper spotlight.
2. Whole Cake Island. I view this arc as definitely above the previous 2 but nowhere near #1. I loved seeing Sanji's backstory (and Reiju is one of my favorite OP characters), and this arc was unique in that, instead of beating the top boss, the Straw Hats had to survive escaping her wrath, showing that the Straw Hats still had a good way to climb before being Yonko level. Luffy vs Kata is my 2nd favorite pre-Wano fight ever (behind Luffy vs Lucci), and we also got to meet the adorable Carrot.
1. Wano. Y'all knew this would be #1. Aside from the BM pirates being sidelined and it occasionally dragging on when it didn't have to, there's little not to love from this arc. Luffy finally became Yonko level (and 2-3 of his crew mates became Commander level), there were 2 amazing Yonko fights in the form of Luffy vs Kaido and BM vs Law and Kid plus plenty of other good fights (like Zoro and Sanji vs King and Queen), the lore we got was amazing, Momo became actually likable and not just a perverted little shit, and even minor characters like Killer and Drake got time to shine.
Asides from the BM pirates being sidelined (minus Perospero and BM herself) and occasional pacing issues, my only real complaint would be that Hiyori should've gotten a chance to fight like her brother and late father, as she was a bit underwhelming in her participation in the final battle. Also she and Zoro should've ******.