We cannot frame future humanitarian interventions (HI) around the failures of Iraq. Not only were there conflicting narratives in Iraq, but it was not purely a HI. Intervention is a relatively novel concept in global politics and we cannot expect it to always have identical outcomes. We must continue to uphold a doctrine of humanitarianism, and attempt to figure out a methodology in how to protect individuals and groups from human rights abuses abroad.
The most important lesson from Iraq may be that we cannot presume to have a crystal ball. The invasion was preventative in nature, under the presumption that Saddam Hussein's past human rights violations would be repeated with new weapons of mass destruction. However, he did not actually have these weapons. Perhaps we should opt for a more reactive policy in HI, rather than trying to predict atrocities before they happen.