Reviewing the 2001 reissue of "All Things Must Pass", for "Rolling Stone", James Hunter wrote of how the album's music "exults in breezy rhythms", among which "the colorful revolutions of 'What Is Life' ... like a Ferris wheel". The following year, in Rolling Stone Press's "Harrison" tribute book, David Fricke included "What Is Life" among his selection of "essential Harrison performances" (just three of which date from the ex-Beatle's solo years) and described the track as an "exultant song of surrender", abetted by Harrison's "pumping fuzz guitar" and the song's "singalong magnetism". AllMusic's Richie Unterberger similarly praises "What Is Life" for its "anthemic" qualities, "particularly snazzy horn lines", and a guitar riff that is "one more entry in the catalog of George Harrison's book of arresting, low, descending guitar lines". Simon Leng credits Harrison's "innate ability to write very fine pop-rock songs" and deems the result "as innovative an exercise in rock-soul as the Temptations' 'Cloud Nine'". Ian Inglis is less enthusiastic, acknowledging that Barham's orchestration and the other musicians give the track "undoubted excitement and energy", but lamenting that the song offers "little overall coherence between words and music". In Thomas MacFarlane's view, "What Is Life" is a "remarkable pop song" that "takes the tone and attitude of Phil Spector's Wall of Sound and channels it through the prism of the late-period Beatles".