What is a critical appreciation of the poem "The Echoing Green"?

"The Echoing Green" is from William Blake's 1789 collection of poems called Songs of Innocence. The poem is Romantic in its simple diction, celebration of the simple lives lived close to the natural world, and the depiction of innocent childhood experiences as recalled by an adult speaker.
The Romantic poets made it a point to write in the language of the common person, and Blake does so in this poem. Simple images like "merry bells ring" conjure a village community in words anyone can understand. The simple schema of rhyming couplets gives the poem a sing-song, comforting, nursery rhyme quality.
What the speaker remembers is an idealized springtime pastoral world in the rural England of yesteryear. The thrush and the skylark sing, while "Old John" sits under a tree and watches the children play. Childhood innocence is highlighted as the children play on the green until they are too tired to do so anymore, at which time they are welcomed by their mothers. They are likened to birds in a nest.
Blake captures the natural innocence some children in society experience, but the poem cannot be wholly understand until read in conjunction with Blake's poems in Songs of Experience, such as "The Chimney Sweep," that show that not all children in England experienced this kind of idyllic life.

In this poem from the "Songs of Innocence" section of his eighteenth-century collection Songs of Innocence and Experience, Blake offers a gentle observation of life over the span of a day in a country setting. A spring morning unfolds to reveal children at play on the "echoing green" while their elders watch fondly and remember their own youth.  The poem ends with the close of day and moves indoors, where families gather in their comfortable, loving homes for a peaceful night's rest.
The poem is comprised of three ten-lined stanzas with five end-rhymed couplets in each. The meter is iambic pentameter, creating a traditional, predictable rhythm that echoes the predictable stages of one's life and the stages of a day, which are both observed in the poem.
Blake's diction is simple and accessible; this is not a poem that requires deep analysis to uncover meaning. The imagery he creates appeals to the senses; the sounds he describes include bells, bird songs, and laughter, and the sights are of children at play, white-haired elders who enjoy their antics, the green, an oak tree, and a sunrise and sunset.
Blake's purpose is to recognize the cyclical nature of life and its simpler pleasures of nature, community, and family.