Playing an overworld without structures can make sense if you have a lava pool and a cave with exposed iron ore. This means you can play Minecraft similar to a casual start, smelting iron ore in a furnace to craft a bucket. A flint and steel will be very useful in this situation since the only way to obtain food this method is to kill animals such as pigs, cows, sheep and chickens. If you light them on fire first with a flint and steel they will drop cooked food, saving time cooking the food in the furnace. You should be trying to do as much as possible while the iron is smelting such as obtaining blocks, building the portal, gathering food, etc.