In the first three stanzas of "MCMXIV," Larkin offers a series of observations about the queues of men enlisting to fight in World War I, the shopfronts and "tin advertisements" of the town, and finally the wheat fields and "flowering grasses" of the countryside. In the fourth and final stanza, Larkin reflects on the innocence of the scenes he has described in the previous three stanzas. Specifically, he reflects upon the idea that the innocence described in the previous stanzas has since been lost, and there will "Never [be] such innocence again." Larkin here is implying that World War I marked a seismic shift, from a prelapsarian time of relative innocence and peace to a time when such innocence can never be experienced again. The fact that Larkin only turns to his reflection in the fourth stanza perhaps implies that he wanted to dwell on, and preserve for as long as possible, the scenes of innocence described in the first three stanzas.
In "Church Going," Larkin follows a similar structure, where he begins with observations and ends with reflection. In the first two stanzas, Larkin describes the interior of the church. He describes the "matting, seats, and stone," the "small neat organ," and the roof, which looks "almost new." In the final two stanzas, Larkin wonders what all these churches, which have "fall[en] completely out of use," will become. He wonders whether they shall be left "to rain and sheep" and whether they will be avoided and deemed "unlucky places." The broader implication, of course, is that organized religion, from Larkin's perspective, seems to be becoming irrelevant and somewhat archaic.
In both poems, the observations with which Larkin begins become the basis or the catalyst for the reflections with which he ends the poems. In "MCMXIV," the observations of innocent scenes prompt the reflection that such innocence might have been lost forever. In "Church Going," the observations of the empty old church interior prompt the reflection that such churches (and the organized religion which they symbolize) have perhaps become, or are quickly becoming, relics of the past.