In his Introduction to From a Cause to a Style: Modernist Architecture's Encounter with the American City Nathan Glazer says that Modernism was not simply a new style in architecture, succeeding neo-Gothicism, neoclassicism, Art Nouveau. Modernism was a movement, with much larger intentions than replacing the decorated tops of buildings with flat roofs, molded window frames with flat strips of metal, curves and curlicues with straight lines. It represented a rebellion against historicism, ornament, overblown form, pandering to the great and rich and newly rich as against serving the needs of a society's common people.
Glazer than adds:

Something odd and unexpected seems to have happened to modernism in architecture and planning: it had broken free from its origins and moorings, drifted away from the world of everyday life, which it had hoped to improve, into a world of its own. From a cause that intended to remake the world, it had become a style, or a family of styles. Modernism had, it is true, produced masterpieces, but it had been incapable of matching the complex urbanity that the history of building, despite its attachment to the historical styles decried by modernism, had been able to create in so many cities. As the older parts of cities were swept away in a wave of urban renewal, as nineteenth-century courthouses and city halls were demolished for modern replacements, more and more people wondered whether what they had lost was matched by the new world being created by modernism.

As Glazer notes the real opposition to the modernist housing project has come not from critics but from the very people that the projects were designed to serve. To the surprise of the enlightened urban planners, people have resisted the attempt to demolish their streets and to sweep away the familiar, the domesticated houses and the small backyards in the inner city. They don’t like living in the air: nor do they like to stand at a window and stare at nothing. They want the life of the street; they want to feel life around them and at the same time to know that they can shut it out and let it in at will.

Cities, unless held together by their ancient fabric of streets and quarters like the cities of Italy and France, or compressed by the kind of centripetal excitement as in a New York and San Francisco, become increasingly alien to those who inhabit them. People then flee them in droves. And yet cities are the nub of social and creative life, and if we flee from them it is into a sterile solitude of suburbia based around the car.

The modernists often did not build for the city, but against it. Thus Le Corbusier’s plan for Algiers first suggested that the old Muslim cities could be entirely refashioned in total disregard of the religious and social needs of the people. Le Corbusier addressed the “problem” of packing people into a city while allowing free movement across it, and his solution was to put highways in the air, with the people placed into apartment blocks beneath them. Ancient homes and corridor streets were to be demolished, and huge tower blocks were to front the ocean, dwarfing mosques and churches.

For modernists architecture is an artform that must be led by its own avant-garde with its utopian tradition. What is delivered in making the city anew is a boring array of unsightly towers around a empty or lifeless open space—the old Bauhaus design is endlessly recycled----and this has been coupled to the strong processes of neoliberalism that have transformed the world we live in.