As I see it, this song can have two interpretations:
David Bowie is referring to his younger self from the Ziggy Stardust/Thin White Duke era. “The speaker was an angel” because it brought him fame and fortune, and some musical quality. This interpretation can be supported by the video of the song:...
[Verse 1]
"You know who I am," he said
The speaker was an angel
He coughed and shook his crumpled wings
Closed his eyes and moved his lips
"It's time we should be going"
[Chorus]
(Waiting so long, I've been waiting so, waiting so)
Look back in anger, driven by the night
'Til you come
(Waiting so long, I've been waiting so, waiting so)
Look back in anger, see it in my eyes
'Til you come
[Verse 2]
No one seemed to hear him
So he leafed through a magazine
And, yawning, rubbed the sleep away
Very sane he seemed to me
[Chorus]
(Waiting so long, I've been waiting so, waiting so)
Look back in anger, driven by the night
'Til you come
(Waiting so long, I've been waiting so, waiting so)
Look back in anger, feel it in my voice
'Til you come
[Outro]
(Waiting so long, ahhh...)
(Waiting so long, I've been waiting so, waiting so)
(Waiting so long, I've been waiting so, waiting so)
(Waiting so long)
Look Back in Anger was written by Brian Eno & David Bowie.
Look Back in Anger was produced by Tony Visconti.
David Bowie released Look Back in Anger on Fri May 18 1979.