Everyone is and can be creative. It is an innate trait stretching back to the first people who picked up a rock to use as a tool. Look at a toddler and tell me some people aren't born with creativity (it is everything else that gets in the way of creativity as we become adults).
If it is impossible to create something new where nothing existed previously, then new things can only be created from the transformation and connection of existing things. In art it can be thought of as making connections between seemingly completely unrelated things or ideas. Prehistoric humans didn't create the rock or the bird they killed with it. They made the connection between the rock on the ground, the bird, and dinner in their belly.
So what is creativity in the photographic sense?
It has nothing to do with visualization, Sorry, Ansel...
If all you are doing is creating things you've already visualized then the actually making of it becomes drudgery, and ultimately unrewarding. You can't learn to see anything new if all you are creating are the images floating around in your consciousness. Even less so if you are hampered by preconceptions, expectations, and rules.
What IS rewarding, and what mastery allows for, is the ability to tap into the images floating around in you subconscious. It is getting to the mental/emotional space for your innate creativity to connect all those ideas and things you have previously seen into completely new ideas—new pictures.
You can call it Zen, the Zone, Transcendence, etc. but all you have is yourself, a tool, and the thing in font of you. And it is up to you to get out of your own way and allow yourself to see the connection between them.