To be honest I think it's by design. They give you options to play as characters involved in the story and they give you the option to play a blank slate with some dialogue options based on their class/race. I think that's more than fine. If you want your own story, it sounds fair that for it to be your own you have to imagine it.
There is a spectrum of freedom they can give the player character in RPGs, sometimes it's a bit more "railroaded" (the Dragon Age games come to mind) and I also like that, but I think for this game this approach works, especially since they give you plenty of options to have a detailed backstory with the origins.
