Luffy and Nika would be the culmination. But if I were to trace a line, the introduction of Joyboy in FI.
Retarded name, brought prophecies into the midst, forcefully connected the One Piece to Robin and WG, meaning, the Pirate King isn’t the freest man in the world, since whoever finds the OP has a duty to fight the WG, for whatever evil thing the 20 kings did in the past. destroyed the sense of adventure pre-ts had, even on a meta level, as the talks of prophecies and JB spurred the communities to focus more on theories of what would happen in the future, rather than focus on the slogfest that was the present. Fuck Fishman Island, it deserves the hate it gets, especially now, that paced the way for the nika fruit retcon.