why does wordsworth highlight the charm and beauty of milton in his work "london"?

The poem has two main purposes, one of which is to pay homage to Milton by saying that he can save the entirety of England with his noblity and virtue. The other purpose of the poem is to draw attention to what Wordsworth feels are the problems with English society.

According to Wordsworth, England was once a great place of happiness, religion, chivalry, art, and literature, but at the present moment those virtues have been lost. Wordsworth can only describe modern England as a swampland, where people are selfish and must be taught about things like "manners, virtue, freedom, power."

Notice that Wordsworth compliments Milton by comparing him to things found in nature, such as the stars, the sea, and "the heavens." For Wordsworth, being likened to nature is the highest compliment possible.