Hall wrote all their music. Oates had a nice voice.
That is not true at all. Oates cowrote, She's Gone, Sarah Smile, You Make My Dreams, I Can't Go for That, Maneater, Adult Education, and Out of Touch, among others. So, that's at least 3 #1 hits, and 4 or more top ten hits. It's ridiculous to say Hall wrote all the music. (Also, Sarah and Janna Allen, and Warren Pash cowrote with Hall.) This is not Simon and Garfunkel.
Hall's problem is not Oates, it's hubris.