Suffering is sometimes the only way to change someone's habits for good, and it takes a whole lot of this painful medicine in The Rime of the Ancient Mariner to make the Mariner realize that all of nature's creations are worthy of love and respect. The entire poem, but especially the middle section concerning the drought, contains enough suffering to last several lifetimes. Our vote for the most cringe-worthy moment is when the Mariner has to bite his arm to wet his black lips with his own blood so that he can yell.
The Mariner's story telling is a part of the penance he must perform throughout his life.
The crew's fate in death is no worse than the Mariner's, who must live on in a state of Life-in-Death. The crew does not receive a raw deal from the powers that be.