It seems Horace wanted to fulfill this injunction, intending his poems to be ‘helpers of humanity’.
Perhaps another reason his poetry endures is that humanity (at least parts of it) is still striving to live meaningfully, joyfully and wisely, and in this (other ‘progress’ notwithstanding), we may not be so distant from the ancients. So perhaps any guidance is reinforced by the reassurance that if we strive, we aren’t alone, we have antecedents and companions to help us on.
‘Horace once said that poetry should be both sweet and useful. Or even true.’
Source: Harry Eyres, Horace and Me: Life Lessons from an Ancient Poet (New York: Farrar, Straus and Giroux, 2013), p. 8