Ideas matter so much, according to critical theorists, because the world is socially constructued by individual human beings whose behavior is mediated by their thoughts; these thoughts, in turn, are shared by the members of a larger culture. Individuals bear responsibility for shaping the world they inhabit. The world around them is not a given that forces itself upon them.
John J. Mearsheimer in The False Promise of International Institutions
Besides the top-down approach, Critical Theory has some great ideas…especially in comparison with Realism.