No, they have to reject ancient tribal beliefs about how the world started, handed down through generations of oral tradition, mixed with slightly less ancient beliefs, and eventually put into text.
They do not have to reject the creator itself.
When I speak of "Creator" I mean the one and only God of the Bible. This Holy Being is completely different from other religion's god(s). So, one does have to reject the God of the Bible, BUT you're right, one does not have to completely rule out a "creator, aliens, lifeforce, whatever" to make a paradigm of their "origin of man" work.