[14] Lacy started working on the album in 2017, recording in his younger sister's bedroom (which he named Paramore Palace) after she left for college, in between sessions he had with other artists, as well as touring with his band, the Internet.

"[6] Natty Kasambala for NME felt that "[Lacy] balances wistful musical throwbacks with authentic lyricism and attitude... From the get-go, [Apollo XXI] delivers exactly what it promises with its stylish, nostalgic artwork: a distinct world filled with hazy strings, warped synths and vocals that range from a flawless '70s-style falsetto to laid-back speech.

Loosely tied together as an intergalactic mission, the album moves with the viscosity of a lava lamp... it's an impressively cohesive introduction to an artist coming into his own.

[22] August Brown of the Los Angeles Times wrote, "With Apollo XXI, Lacy's finally come into his own as a solo artist, one straddling R&B, indie rock and his own idiosyncrasies.

[Apollo XXI] has a relaxed, lived-in skillfulness that shows the handiwork of a veteran player... it's quintessentially L.A. in its mix of retro funk, twitchy beat music and even occasional canyon-rock vibes.