[1] In regards to the project, she expressed desire to collaborate with an all-female creative team, differing from her previous experiences while recording her fourth studio album, Love + Fear (2019).

[2] Following the release of the lead single, "Man's World" in 2020, Marina posted several teasers of other songs from her fifth album's recording sessions, such as "Flowers" and a clip from a track about Venus flytrap plants.

"[5] Due to the song's use of "theatrical vocal riffs and hard-rocking strings", Joey Nolfi from Entertainment Weekly called it similar, musically, to the material on Marina's debut album, The Family Jewels (2010).

[16] Marina switches between singing in "theatrical soprano" to "belligerent sass-mouth" during the verses, which Thomas H. Green of The Arts Desk found to be gutsy and trite.

[17] According to Gab Ginsberg from Billboard, "Purge the Poison" is "an Earth Day anthem of sorts", due to its lyrics pertaining to climate change and saving the planet.

[13][18] As Mother Nature, she opens the song, addressing events such as United States wars, and the consequences of the COVID-19 pandemic: "Virus come, fires burn / Until human beings learn / From every disaster / You are not my master.

"[19] Other lyrics in the song reference memorable popular culture events, such as Britney Spears shaving her head in 2007, and Harvey Weinstein's role in the Me Too movement.

[12] Dimitra Gurduiala from Atwood Magazine acclaimed "Purge the Poison", writing that it is the "perfect combination" of her previous musical endeavors; she continued: "If we didn't already know what Marina was able to do, it would be hard to believe that such an iconic and catchy song came out while dealing with serious issues that touch each of us every day.

[18] Red Dziri from The Line of Best Fit highlighted Marina's vocal abilities on the song, writing that she "confront[s] turbulence with ease and get[s] her every word in despite the constant menace of being overthrown by an instrumental neurosis.

"[20] On the other hand, Abigail Firth from Dork referred to "Purge the Poison" as the "biggest misstep" of Ancient Dreams in a Modern Land; she called the song "too on the nose" and inferior to its surrounding tracks "Venus Fly Trap" and "Man's World".