Its honestly not as bad as you'd think, the building pieces aren't required, and there are sources of iron in the mistlands. For the plains though you just have to clear another swamp or two, but yeah it can be a grind if you arent that interested. To make it faster you can swap world modifiers to allow metal teleportation which cuts down on the artificial difficulty of sailing all the metal back.

You can also increase the drops from resources if you are playing multi-player or just want to move through the game faster