Green’s Dictionary of Slang

(Aus.) very stupid and/or inadequate.

1999		G. Seal Lingo 127: There are [...] subtle gradations in the types of stupidity, thoughtlessness, hopelessness, incapacity and sheer ineptitude that may come in for verbal censure. A person may be: [...] not in the race.
2013		T. Peacock More You Bet 8: Someone who might have been regarded as not good enough for something or someone [was] ‘not in the race’.