That's just the way the US system is set up. You can't win the presidency by doing really well in the five largest states.
I don't think you should be able to win the presidency by doing really well in the five largest states necessarily, but I definitely don't think you should be able to win the presidency by only doing well in a couple of swing states.
Whenever you have voting you have swing votes. That's just Democracy. If it wasn't swing states it would be swing voters nationwide.