"Doomsday" evolved from a song that was originally part-written by former Architects lead guitarist Tom Searle during sessions for the band's seventh album All Our Gods Have Abandoned Us.

[6] Writing for Noisey, Tom Connick explained that the song "is about [Dan's] conflicted feelings regarding the loss, and is a marker of Architects' poise in the face of extreme sadness".

[13] Speaking about the "acoustic piano ballad", Searle suggested that the song "needed a rendition that exposed the sadness behind the lyrics", which he claimed vocalist Sam Carter delivered "beautifully".

[16] According to Zoe Camp of Revolver magazine, it "finds the band members tearing through the song against a starry backdrop, performing so intensely that, at times, they appear to break apart themselves".

[5] Metal Hammer columnist Eleanor Goodman described it as "a moving video featuring Tom's twin brother, drummer Dan, suspended in the expanse of the universe".

[14] Clash writer Robin Murray called it "simple, sparse, and really rather beautiful", praising Sam Carter's "rather special" vocal performance.