What does the above quote from the deserted village, lines 51-56, mean?

That England forgot about it's previous self

Explanation:

Quote on lines 51-56 from the 'deserted village':

Ill fares the land, to hastening ills a prey,

Where wealth accumulates, and men decay:

Princes and lords may flourish, or may fade;

A breath can make them, as a breath has made;

But a bold peasantry, their country's pride,

When once destroyed can never be supplied.

Answer:

The poem tell us that in the process of people exploring the riches of the countryside, the earth was misused leading to it's destruction.

It gave an example of a worker who was interested in the gains of the land and while at it destroys it. It emphasized the loss of pride in the land a person toiled.

Thus, England never remained the same.