"[3] According to Pitchfork's Laura Snapes, the singer admits to having been selfish in the past, revealing a willingness to welcome love back into her life that "reverberates" throughout the song's verses.
[3] Described as battle between head and heart, Danielle's vocals are eventually joined by those of her sisters, who support her decision once she "stops explaining herself" and ultimately "pleads her case from the rooftops".
[4] However, Kornhaber observed that its title could refer to Haim fans who have been craving the band's return during the four years since the release of their debut album, boasting a sound that is both similar to and different from their previous work.
[4] A pre-chorus follows, which Kornhaber identified as "a less intense rendition of the chorus";[7] Danielle's line "I'll take the fall and the fault in us" reinforces its parent album's theme "that relationships are hard", according to The Guardian critic Kitty Empire.
[7] Other instrumentation includes "power ballad–worthy piano chords" and "pitch-shifted vocal riffs";[10] the song also features some animal sound effects, which music journalists have identified a horse's neigh and seagull cries.
Snapes observed that the single resembles the works of Don Henley and Christine McVie of The Eagles and Fleetwood Mac, respectively, until "the chorus swells and shudders like Lindsey Buckingham at his most overheated, sprinkled with jittery digital chatter.
"[3] Meanwhile, Kornhaber described "Want You Back" as a retro combination of 1980s and 1990s pop music that resembles the work of Fleetwood Mac, Prince and, albeit to a lesser extent, Def Leppard.
"[7] Pitchfork ranked "Want You Back" the 72nd greatest song of 2017, with contributor Olivia Horn writing that Danielle's vocals "achieve a rhythmic flow that simultaneously flexes her strengths as a lyricist, vocalist, and percussionist.
[11] Comparing the music video to the work of director Martin Scorsese and the film Foxes, Willman concluded "If anyone can bring sexy back to Sherman Oaks, it’s Haim.