NEW YORK — Since the Museum of Modern Art moved to 53rd Street in 1939, it has been expanded several times, gobbling up whatever space it could find in one of this country’s densest urban neighborhoods. It has also struggled over the past decade with extraordinary demand, with some years topping more than 3 million annual visitors.

On Oct. 21, after an almost five-month closure, the museum will open yet another major expansion project, adding 40,000 square feet of gallery space for a total of some 166,000 square feet. They’ve also reconfigured the old galleries and reinstalled the permanent collection.

All this growth has come at a cost. When the museum was founded in 1929, it put forth a militant face, arguing by example for a modernist view of the world that eventually encompassed art, architecture and design. But it was always an establishment property, loyal to wealth and wealthy donors, and though the public embraced it, the museum often did things that felt like a betrayal of its larger, public mission. It became a bastion of exclusion, and artists and curators who were not welcome there often worked and organized in opposition to what MoMA stood for, pushing the art world forward even as one of its greatest “modern” institutions held things back.

When the latest plans for expansion were unveiled in 2014, MoMA announced it would demolish the former American Folk Art Museum, which it had acquired, designed by the respected firm of Tod Williams Billie Tsien Architects (the same group that is working on the design of the Barack Obama presidential center in Chicago). Protest was vigorous but to no avail. MoMA gets what MoMA wants, and a perfectly good building was destroyed to make room for a purpose-built structure.

Visitors to the new campus will be happy for the extra space and the much-improved circulation of the galleries. The expansion, designed by Diller Scofidio + Renfro in collaboration with Gensler, includes both a new building where the old Folk Art museum stood and space carved out of the dark, enormous and architecturally dispiriting condominium tower designed by Jean Nouvel at 53 W. 53rd St. (there’s a penthouse apartment still available for a mere $63.8 million). Galleries now flow through all three spaces, the old building, the new one and the lower floors of the Nouvel tower.

That means there is less going up and down the escalators than was necessary in the old configuration, and there was nothing quite so depressing as the MoMA escalators. They felt tight, constrained and overcrowded, but it was always easier to take them than to wait for the elevators. If you wanted to see two shows, they were inevitably not just on different floors, but several floors apart. The intellectual energy of the galleries fizzled out in this strangely uncongenial, vertical space that was reminiscent of a shopping mall.

Now, there is a second way to move between the floors: a capacious steel staircase that floats in a well-lighted column of space facing 53rd Street. That, alone, would make this renovation welcome. But the increase in gallery space also helps bring order to the collection, even as the museum works to mix things up stylistically, chronologically and across disciplinary lines.

The collection is still roughly arranged by date, with the oldest work (from the late 19th century) on view on the fifth floor, mid-century work on the fourth and the newest material on the second. More gallery space means more options for dealing with light-sensitive material and film and video, which have now been thoroughly integrated into galleries. The museum has also added free galleries on the ground level, a small concession to those put off by the $25 full admission, and a welcome break from the erstwhile hermetic relationship to the street and city beyond.

Visitors will enjoy all of this, as well as a new cafe with outdoor seating on the sixth floor, a new metal awning over the 53rd Street entrance, a more open and sensible ticket and entry atrium, reopened windows into the central lobby at the core of the old building, and a double-height “studio” space in the new wing, for performance and installation works.

The museum has also committed to regularly rotating its permanent collection, to get more of it on view and incorporate diverse artists into what was for decades a rigidly canonical approach to display. Every six months, one-third of the collection will be switched out, with the galleries fully refreshed every 18 months.

MoMA is billing these changes to the display of the art as the most significant aspect of the expansion. Not only is the museum growing, it is changing its relationship to the art, no longer insisting on a single grand narrative, no longer teaching, but simply opening itself up to exploration and discovery. “The museum is not the place where we are going to give a lesson,” Christophe Cherix, chief curator of drawings and prints, told The Washington Post last summer.

That’s radical, and to abandon the idea that the museum serves an educational function would be a disaster. But, though such language may sound good to other museum professionals, the public generally does want a lesson. And despite efforts to abandon “grand narratives,” people generally revert to them, at least to provide a general intellectual skeleton on which to hang their observations and discoveries. Up on the fifth floor, the galleries aren’t labeled by the old “isms” of art history — Fauvism, expressionism, cubism, surrealism — though the works are mostly grouped by stylistic or intellectual affinities. Ordinary visitors will probably use their handheld devices to look up and fill in the labels that have been removed, reconstructing the more linear sense of art history that the curators have attempted to dissolve.

Much of the best of MoMA’s work over the past decade has been about adding to the larger narrative of modern art, discovering different “modernisms” around the planet and expanding the definition of what qualifies as art. An exhibition of Tarsila do Amaral extended the drama of modernist painting into Brazil, where it flourished, while a display of the sculptures of Bodys Isek Kingelez connected an artist working in the Congo to the larger history of architecture and utopian social thinking. And it’s good to see works from these artists incorporated into the display of the permanent collection.

But there’s a difference between complicating narratives and abandoning them. MoMA seems to want to do the latter but can’t quite bring itself to do so. The rough narrative in the galleries remains broadly chronological, with the stars of its collections still pretty much where you expect to find them. The danger is that the museum will end up with a two-tier system, still dependent on the iconic pieces that visitors demand to see, supplemented by the occasional guests brought in temporarily to complicate things. Even more worrisome is the stated goal of abandoning the didactic function. No one wants a cultural organization that hectors, but they do want to learn. It’s a question of tone.

And it’s not entirely clear at whom the new installation is aimed: the ordinary visitor who is supposedly demanding to see art without any supporting intellectual apparatus or the more sophisticated audience who will understand why it’s interesting to, say, hang a 1967 Faith Ringgold painting near Picasso’s 1907 “Les Demoiselles d’Avignon.” Some of these juxtapositions are telling and smart; others seem merely clever.

Now MoMA faces the same challenge it faced before: how to manage its own success. Like widening highways, which tends to simply induce more traffic, expanding MoMA will only make it more attractive to more people. The new building may handle the crowds well for a while. But MoMA has become one of the great “winner takes all” cultural institutions, and the more it grows, the more it will feel the need to keep growing. And, with that, the pressure to do the big, dumb, crowd-pleasing shows like the terrible 2015 Bjork exhibition will only increase.

At some point, if the institution is to remain genuinely relevant to the discourse of art, it will have to grapple with this cycle and interrupt it. That will mean recommitting to first principles, or at least some principles that reference not just access to art, but the actual experience of thinking about it. MoMA knows how to get people through the door, but no one seems terribly concerned with what happens when they leave. Did their eyeballs simply lounge over lots of intriguing things, or did they learn something?

The Museum of Modern Art, at 11 W. 53rd St. in New York, reopens Oct. 21.