Modernization was used by social scientists in the 1950s and 1960s to refer to the process by which "primitive" societies (i.e. non-western) would become "modern" ones (i.e. westernized). This evolutionist view has an implicit assumption that all societies will become like the west, and that this represents progress, and is positive.
This view was challenged in the 1970s by theorists, many from Latin America, who believed instead that the world is a global system. In their view, the west developed by exploiting the third world. The west forcibly extracted human and natural resources from the third world, thereby ensuring western development while rendering the non-west underdeveloped. So influential has this idea become that we usually now refer to development, not modernization, and call "third world" countries undeveloped, underdeveloped, or less developed (and least developed, for the poorest countries), rather than primitive.