“Disgraced” was far from perfect when it opened off-Broadway two years ago, but it worked up to a point. Aasif Mandvi, of “The Daily Show,” was astringently effective as a Pakistani- American lawyer testing the limits of assimilation.

Sure, Ayad Akhtar’s script was didactic, but at least it went for the jugular — and ended up winning the Pulitzer Prize. Now “Disgraced” is back, with a new cast, on Broadway at that. But the bigger stage hasn’t been kind to the show.

Because the play seems like a PowerPoint lecture about current hot topics — terrorism, Islam, Jews, religion, art — it requires excellent acting. Pity the performances here are wildly uneven, and a couple of them are downright bad.

Purists may look suspiciously at Josh Radnor, the “How I Met Your Mother” star who’s helping the show’s commercial prospects. But Radnor’s actually quite good as Isaac, a smarmy, smug Whitney Museum curator — and Karen Pittman, the original cast’s lone survivor, is even better as Isaac’s no-nonsense wife, Jory.

No, the problems are Hari Dhillon and Gretchen Mol. Inconveniently they play the leads, attorney Amir Kapoor and his wife, the WASP-y painter Emily. And they’re never believable — either as a couple or as, you know, people.

When Amir poses for Emily’s portrait, Dhillon can’t even meet her eye, his gaze vague and unfixed. Their kisses lack heat, and when they speak, they sound like actors reading lines.

Amir is a complex role. An immigrant success story who’s angling for partnership at his law firm, he claims to be Indian (which is more palatable than Pakistani) and has rejected Islam — he calls the Koran “a long hate mail letter to humanity.” This creates friction with Emily, a well-meaning, rather deluded liberal who finds inspiration in Islamic art.

After things come to a boil during a nightmarish dinner party — limply staged by director Kimberly Senior — all four main characters are changed for the worst.

Though religion takes up a lot of time in “Disgraced,” the play is sharpest in what it says about ambition and the things people will do to get ahead. Akhtar’s portrayal of Manhattan’s entitled elite often is deliciously mean — that it comes through in this declawed production says a lot.