Yes, a stone thrower will never win against a tank, it doesn't matter how many stones he has. Similarly, if you only have a 100 rockets, but the enemy has enough interceptors or capacity to absorb them, you will lose. In both cases, one side is massively superior to the other and such math is basically irrelevant. Where math enters the picture, is when you have an actual comparable opponent. That's when you need actual strategy and tactics. And that's when focusing on missile defense becomes a bad move.