If "purpose" is simply the intent of a creator, the words used to describe what the creator intended when they created, then I don't see the great loss in not having it.
Imagine your father always wanted a child, and for the child to take over the family business. Is your life without merit, utterly void of value, if you become a fireman instead? After all, you are not fulfilling the purpose, the intent, of those who created you. Anything outside their specifications is meaningless nihilism, right?
Personally, I think there is more to "purpose" than this definition, it's a very small definition that does not truly compass what people mean when they talk about purpose.
Likewise if God made me to, say, love and forgive others, I can either serve my purpose or not. But the purpose is given to me by the intent of the creator.