I think people are vastly overestimating that comment he made 2 years ago. There is far more plot/characters outside of wano than inside. Blackbeard and Shanks are far more important Yonko than Kaido/BM. You have the World Government, Revolutionaries, Marines and a variety of other factions that need to be addressed. You also just have the pure fact that sheer escalation needs to happen again to even get us to the final war.
Remember, the goal to fight Kaido started 350 chapters before fighting Kaido. It escalated to what it was today. Not saying it will take that long, but don't be surprised if the next arc only slowly begins the track of designing the endgame of this series. Luffy won't join a war immediately. He still has a final road Poneglyphs and laugh Tale to find. And who knows what else Oda tackles in the midst.
It's the same reason I tell people to buckle up for spending more time than you think in Wano the next year or so lol. There is way more that needs to be resolved beyond the rest of the fights.
And i think a lot of people overestimate how much it will take to deal with a lot of those things you just said. It's not just a comment Oda made 2 years ago, he has been doubling down on this year and % of the story a few times.
I'm pretty sure the end of Wano and the information we will get about what happened outside will sped up the events of the story dramatically.
Many things will have happen without the presence of the Straw Hats.
There's a lot of shit going around the world while Wano is happening.
Warlords running, World Governament readying their "cleasing", the shit that happened in the Reverie, Blackbeard and Shanks move.
We don't need to be a part of a lot of these things. Even if we wanted to.