The song contains an interpolation of "I'm Caught Up in a One Night Affair" written by Patrick Adams and Terri Gonzalez, both of whom received songwriting credits as a result.

A disco revival song, the lyrics are about Carey being dissatisfied by her lover's failed attempts at romancing her.

"You Don't Know What to Do" garnered critical acclaim amongst music critics: many complimented the disco revival and throwback style, calling it the best track on the album, and compared it to the works of Jocelyn Brown, Daft Punk, Chic and post-revivalist songs produced Pharrell Williams.

"You Don't Know What to Do" was written by Carey, Jermaine Dupri and Bryan-Michael Cox, with featured artist Wale.

[17] Several critics highlighted the track as following in the recent disco revivalism footsteps of Daft Punk, Justin Timberlake and posthumous Michael Jackson material.

[16][18] The song begins with Carey singing about how she is in a dilemma as to whether or not she wishes to stay in a relationship with her lover, as he is no longer capable of romancing her.

[19] Pitchfork Media writer Jordan Sargent compared "You Don't Know What to Do" to Carey's previous singles "Fantasy" (1995) and "Heartbreaker" (1999), but noted that it felt like a "logical extension of post-Pharrell disco revivalism".

[20] Christina Lee for Idolator thought that the 70s disco feel embodied Daft Punk's 2013 single, "Get Lucky".

[14] Billboard writer Kenneth Partridge complimented the song for its dance appeal, adding that the only thing missing was a cameo from Nile Rodgers.

[15] Entertainment Weekly writer Melissa Maerz complimented the interpolation of "I'm Caught Up in a One Night Affair", describing it as "nostalgic", and further stated that Carey embodies the "bravado" of American singer Jennifer Holliday in the broadway musical Dreamgirls.

[23] Digital Spy's Lewis Corner praised Dupri for producing a piano "disco stormer" with throwback appeal.

[24] Mike Wass of Idolator thought that "You Don't Know What to Do" would have been worthy of being recorded by American disco singer Donna Summer.

[25] Jordan Sargent of Pitchfork Media praised its composition and noted that the disco and gospel genres are where middle-aged woman can "thrive", whereby Carey "fits in unsurprisingly well".

[16] Similarly, Aisha Harris of Slate Magazine praised the song's production and Carey's vocals too, but also thought that Wale's rap verses were not required.