Wynn Harmon, as James Jarvis, comforts Eric Owens, as Stephen Kumalo, in the Washington National Opera’s “Lost in the Stars.” (Karli Cadel/for the Washington National Opera)

Is Kurt Weill’s “Lost in the Stars” theater or opera? The question has been debated since the work’s premiere on Broadway in 1949. When it comes to the Washington National Opera’s production, which opened Friday at the Kennedy Center’s Eisenhower Theater, let’s call it both: The Washington Post’s chief theater critic, Peter Marks, is reviewing it as well.

In practice, the labels “opera” or “musical” don’t really matter in appraising this hybrid, flawed work. All that can be said for certain is that “Lost in the Stars” is not what it palpably longs to be: a great American vernacular opera-musical about race relations, transforming Alan Paton’s novel “Cry, the Beloved Country” for the stage in a final masterpiece. (Weill died the year after it opened.) At best, it’s a noble failure.

And WNO’s production by Tazewell Thompson (already seen in Cape Town, South Africa, and the Glimmerglass Festival in Cooperstown, N.Y.) proved equally uncertain. The weaknesses weren’t where you would expect. The spoken dialogue was better than the opera-company norm — as far as “better” can apply to Maxwell Anderson’s preachy and dated text, delivered in assumed South African accents. (Unobtrusive floor amplification increased audibility.)

But musically, despite the assured conductor John DeMain, the evening kept falling short. The songs of Irina, a young woman whose boyfriend, Absalom, receives the death penalty for killing a white man, need something stronger than the gentle lyricism of the operatic soprano (and WNO debutante) Lauren Michelle. Linda, a good-time gal with one show-stopping number, needs to be a Broadway belter, but Cheryl Freeman, despite a starry résumé in musical theater, didn’t have strong enough pipes. Even the star bass-baritone Eric Owens as Stephen Kumalo, the country pastor whose faith is shaken by his son Absalom’s crime and punishment, didn’t quite muster full physical or vocal authority — indeed, he sounded oddly muted, particularly at the top of his voice, and kept shrinking into his body rather than inhabiting it.

Directorially, too, Thompson took an overly respectful approach to a work that needs a strong and critical hand. “Lost in the Stars” incorporates several songs Weill and Anderson wrote for a different show in the late 1930s; none of them, including the title number, quite fit their new situations or helped the characters become less two-dimensional.

Thompson, who also directed WNO’s “Appomattox,” has shown he can be an effective storyteller and work with simple sets — here, Michael Mitchell’s rusted corrugated-metal walls, with lots of dramatic shadows (lighting: Robert Wierzel). But those shadows, or the stars that appeared at the climax of the title song, only augmented the work’s heavy-handedness.

There were a few highlights. The tenor Sean Panikkar, as a narrator figure called the Leader, sang well and became a dramatic fulcrum by default; and the young Caleb McLaughlin, as Stephen’s nephew, Alex, aced a solo song and dance number in the strongest performance of the night.

And the actor Wynn Harmon was respectable as James Jarvis, whose son is killed by Absalom — and whose role yields the show’s most tone-deaf moment. As Stephen sits in his church in the last scene, waiting for the hour of his son’s execution, Jarvis barges in and explains that he now understands the importance of overlooking racial boundaries and becoming friends. Although true to Paton’s plot, on stage this seemed less a poignant image of racial reconciliation and more another example of a white man assuming power in a relationship with a black one. In the 1974 movie, Stephen (Brock Peters) rebuffed Jarvis’s overture. Opera companies aren’t as free to rewrite the works they present, but a sense of historical distance wouldn’t hurt.

“Lost in the Stars” continues through Feb. 20 at the Kennedy Center for the Performing Arts. kennedy-center.org.