According to Matthew Arnold in The Study of Poetry, Geoffrey Chaucer does not rank among the greatest poets because, although he is a master of storytelling and poetic charm, he lacks "high seriousness."
Arnold acknowledges Chaucer's brilliance in narrative skill, vivid characterization, and natural ease in poetry.
However, he believes that Chaucer’s poetry does not possess the moral depth, sublimity, and profound philosophical insight that characterize truly great poets like Homer, Dante, Shakespeare, and Milton.
While Arnold appreciates Chaucer’s contributions to English poetry, he sees his work as more focused on delight and entertainment rather than conveying the profound truths and moral gravity that define the highest forms of poetry.