I've been playing Dungeon World for a while and I encourage players to collaborate to make the game really "our game" by using the principles to the letter. But when I look back at the world we created, it looks nothing like a coherent settings. I think this is the consequence of improvisation mixed with cooperative storytelling with a lack of central theme. The world we created is weird and crazy and there's no way that I can get my head around it. That's basically where we are right now. I don't understand the setting I'm supposed to portray.
I'm about to start another game of Dungeon World and this time I want to keep things simple. By simple I mean something that you would recognize as something Tolkien, G.R.R. Martin or Salvatore would have written. The main reason is that I'd like to avoid dealing with moon dwarves fighting orcs wearing jetpacks again. Some of my players told me that was the downside of the last campaign. It went too far on the crazy side. I have a mix of crazy and more vanilla players (what I consider vanilla is tolkienesque) in my group and I want to make sure things stay "under control".
TL;DR
So we've been playing Dungeon World using improv and cooperative storytelling and now my world is populated by jetpack-wearing orcs fighting moon dwarves and wizards are known to be lactose intolerant. How can I prevent this kind of sidetracking in my next game of Dungeon World?