The base building is not too grindy actualy. But it's not really explained how everything works. You can scrap a ton of stuff in the settlements to get lots of wood and steel: Trees, cars, even whole buildings. Rare materials you can either produce yourself or buy in bulk from traders. For example adhesive can be cooked from tomatoes, corn and mutfruit. So just let your settlers produce some more then what they need for food. Easiest way to have something to trade with for rare materials is to produce extra water.
Also you don't have to find materials for each new settlements from scratch. With the local leader perk you can create supply lines between your setllements so you have access to all your crafting materials from each workbench.
Another thing that helps is to unload your junk to your companion if it gets too heavy while you're questing. You don't have to scrap it afterwards. Just throw it into a workbench to get new materials.