What is the importance of the ending of Lord of the Flies, other than that it is ironic?

At the end of Golding's novel, the boys are forced to finally face the reality of their actions on the island. The naval officer who comes to their rescue recognizes that the boys are playing at war and asks if any are killed. Ralph admits that two boys have gone, referring to the deaths of Simon and Piggy; however, he fails to include the boy with the mulberry birthmark that they lost in their first failed attempt at a signal fire. In fact, this first loss of life was never entirely acknowledged by any of the boys. 

The officer also wants to know who is in charge and expresses his dissatisfaction that a group of British boys could not keep it together better. In response, Ralph claims that they were civil at first, but his speech is cut short as he is overcome with emotion. Golding writes that Ralph "gave himself up to them [sobs] now for the first time on the island." One can infer that Ralph, and the others who eventually join him in his grief, has finally realized the gravity of their situation and the results of their actions.  Golding explicitly states that the boys are grieving the loss of their innocence on the island. No matter what happens next, they can never go back to being the young boys who once saw their island home as a shimmering, exciting adventure.