Is the poem "The Darkling Thrush" gloomy?

Hardy's "The Darkling Thrush" was intended as a poem on the death of the old century—the nineteenth. Certainly, there are gloomy elements within it, with the initial few stanzas describing the "spectre-grey" frost and the "desolate" day's-end atmosphere. The landscape is devoid of people, as all have "sought their household fires," and its emptiness helps give the impression of its being "the Century's corpse." A semantic field of death pervades, with such words as "crypt-like," "death-lament," "shrunken," "spirit," and "fervourless."
The gloom, however, does not remain. On the contrary, Hardy explicitly states that the thrush "had chosen thus to fling his soul / upon the growing gloom." The gloomy atmosphere cannot remain in the face of this "joy illuminated" as the thrush begins to sing. Its "ecstatic sound" is representative of "Hope," heralding the new century and a new beginning. Ultimately, then, the tone of the poem is optimistic and anticipatory, looking forward to positive change.