I'm not sure Bioshock Infinite was really about one thing. Only about 5% of the game is a story about stories. Most of it is a story about a woman learning to be her own agent rather than a means to other people's ends, and after that it's about the question of self-determination versus fate (this is pretty much the Lutece Twins' entire role). It begins and ends on the note you're talking about here, but those themes don't really seem to be as pervasive as the themes of The Grapes of Wrath.