No, it couldn't have. It's one of the nouns that requires use of go in situations like this.
From Gramadach na Gaeilge:
> Some subjective adjectives of assessment take the adverbial partigle go when used with the verb bí (they're kind of seen as "adverbs of the verb bí")
Others include: maith, álainn, dona, aoibhinn, breá, olc, and iontach.