If in Kanto, Ash didn't get participation badges, defeated Ash defeated Team Rocket (I mean the whole organization), fought and beat the Elite 4, and had a final showdown with Gary afterwards, wan't the star of Johto, Pokemon would've been a much better anime.
For me, Lucci would be at the top of the Grand Line boss fights while Doflamingo would be at the bottom. I don't count Katakuri as a boss, but if I had to place his fight anywhere, it's above Doflamingo's for sure.
Wano Arc will end with having Luffy barely surpassed Kaido. By that, I mean say Kaido is 100, Luffy would be 98. By the next arc, he'll be more refined and beyond Kaido. It's no different from Katakuri.