I wouldn't say anything that happens in the main plot happens without Luffy. Background, world-building stuff? Sure. .
There's actually a lot more shit than you think:
- The Payback War (basically Blackbeard Pirates vs. remaining Whitebeard Pirates), Blackbeard became one of the Four Emperors that way.
- Four of Luffy's rivals going into Big Mom's territory and getting wrecked. We actually see Urouge recovering from that battle in a chapter released two years ago in publication in the chapter that introduces Kaidou, despite his encounter with Big Mom not being mentioned till much later.
- Aokiji vs. Akainu's battle on Punk Hazard to determine who would take Sengoku's place that last 10 days straight. Akainu became Fleet Admiral due to this.
- Blackbeard's raid of the Revolutionary Army HQ.
There's a multitude of other examples, but every single one of these events are major events that affect the course and direction of the story that could've been entire arcs in of themselves if Oda really wanted to do that. Of course that isn't including all of the various atrocities and wars that are being waged across the One Piece world as well, which is happening co-currently with the main cast and Luffy isn't doing anything about it due to having his own ambitions. If it was Dragonball the ONLY islands that would be facing problems would be the ones Luffy is currently in. Kind of like how in the Namek arc the ONLY planet facing a planet-destruction event is Namek and it's from the literal Emperor of the Universe.