[5] The Daily Telegraph called it "a smart, swaggering break-up album from a major talent",[9] while The Independent said Lewis "adds a California sheen to melancholy and nostalgia".

He said Lewis, "the rare 21st-century singer-songwriter whose level of craft renders her good enough for 76-year-old master drummer Jim Keltner", "loses the spring in her step that made her so 21st-century by proving it", naming as highlights the title track, "Rabbit Hole", and "Dogwood".

[16] In a year-end essay for Slate, Ann Powers cited On the Line as one of her favorite albums from 2019 and proof that the format is not dead but rather undergoing a "metamorphosis".

She added that concept albums had reemerged through the culturally-relevant autobiographical narratives of artists such as Lewis, who "confronted the ghost of her mother by invoking the musical touchstones they had shared in the fearless On the Line".

[17] A month prior to the album's release, Ryan Adams, who helped produce the record, was accused by several women of sexual misconduct.