“Berlin Free-Zone 3-2,” a 1990 proposal by Lebbeus Woods for an abandoned government building in reunified Berlin. The structure, more theoretical than practical, has no assigned purpose.

These are lonely times for Lebbeus Woods.

In the early 1990s this irreverent New York architect produced a series of dark and moody renderings that made him a cult figure among students and academics. Foreboding images of bombed-out cities populated by strange, parasitic structures, they seemed to portray a world in a perpetual state of war, one in which the architect’s task was to create safe houses for society’s outcasts.

Since then Mr. Woods has become his own kind of outcast.

Architecture is big business today. While most of his friends and colleagues have abandoned their imaginary cities to chase lucrative commissions, Mr. Woods has shown little interest in building. Instead he continues to work at a small drafting table in a corner of his downtown apartment, a solitary, monklike figure churning out increasingly abstract architectural fantasies, several of which are on view in the “Dreamland” show at the Museum of Modern Art.

Some question the wisdom of his choices. (They certainly haven’t made him a rich man.) But that he now stands virtually alone underscores a disturbing shift in the architectural profession during the past decade or so. By abandoning fantasy for the more pragmatic aspects of building, the profession has lost some of its capacity for self-criticism, not to mention one of its most valuable imaginative tools.

Not so long ago many of the world’s greatest architectural talents behaved as though the actual construction of buildings was beneath them. During the 1960s firms like Superstudio in Florence, Italy, and Archigram in London were designing urban visions intended to shake up the status quo. These projects — walking, mechanized cities and mirrored megastructures that extended over mountain ranges and across deserts — were stinging attacks on a professional mainstream that avant-garde architects believed lacked imaginative energy.

When I was an architecture student in New York in the early 1990s, the architects my peers and I admired most were famous for losing competitions, not winning them. For us it simply meant that their work was too radical, too bold for the cultural establishment.

This was not just youthful idealism. Free of mundane professional considerations like budgets, clients and zoning laws, these architects were able to produce works that were aesthetically inventive and piercing social commentaries. And their designs were wildly influential, closely studied by younger architects who sought to apply their ideas in the real world.

Mr. Woods, now 68, was a regular fixture of that scene. In the early 1990s he published a stunning series of renderings that explored the intersection of architecture and violence. The first of these, the Berlin Free-Zone project, designed soon after the fall of the Berlin Wall, was conceived as an illustration of how periods of social upheaval are also opportunities for creative freedom.

Aggressive machinelike structures — their steel exteriors resembling military debris — are implanted in the abandoned ruins of buildings that flank the wall’s former death zone. Cramped and oddly shaped, the interiors were designed to be difficult to inhabit — a strategy for screening out the typical bourgeois. (“You can’t bring your old habits here,” he warned. “If you want to participate, you will have to reinvent yourself.”)