| Quote #1
Let not Ambition mock their useful toil,
The speaker seems to expect the reader—at least, rich, snooty readers—to look down their noses at the lives of the poor because they didn't accomplish anything worthy of being recorded in the history books.
| Quote #2
Full many a flow'r is born to blush unseen,
The speaker uses a metaphor, though, to point out that some of the poor people buried here might have been worthy of being recorded in history books, but never had the opportunity. They wasted their lives in the "desert air" of their tiny village and were never recognized by the wider world.
| Quote #3
Some village-Hampden, that with dauntless breast
There could have been someone like John Hampden, a man who stood up to the tyranny of the king, living in this village, only no one ever wrote down what he did. Does that make his accomplishments any less valid or legit?