Not really. If you have a fire user, and I am in a corner what stops you from setting the building on fire to get me out of my hole and into a better place for you to engage me? If you use water what stops you from creating some water effect or darkness or any of the other magics people have. If you are locked in melee person but have a shield that can stop a giants blow, yeah you can move in and be safe. If you are a flier, well then I hate you because either I come out or it becomes a draw. There are many, many ways to fight a gun fighter. The issue is most people don't actually think and use the terrain to their advantage while gun fighters have to.