Creating an entire world can be hard. Unless you really know what you’re doing, you’re very likely to create something quite unrealistic. For example, a common mistake when drawing rivers is to make them fork downstream, which almost never happens in reality. Is that really a big deal? Maybe not, but I find more realistic spaces make for more believable stories. The more about the world that makes sense, the easier it is to improvise when your players (inevitably) go off the rails.
It’s also just a LOT to create all at once. You are deciding every major geographical feature of your world in one go, which has a cascade effect down to where cities and towns are built, what kind of terrain you have, what kind of people live where, and what kind of adventures you have.
This is just a long way of saying that instead of hand drawing this map, I built it with ProFantasy’s Fractal Terrains. I added the pretty colours and clouds with the Terraformer plugin to give my players a nice, brief, view of the plane before they entered it and started the game proper. I also used this map as the basis of every other overland and town map I have created for the campaign. Having this huge world map ready to go has made every thing else much easier to create and keep track of.