The doctrine of humanitarian intervention is wholly admirable but completely impractical. Much like many of the moral problems we face—poverty, healthcare, and climate change—there are often huge logistical hurdles to overcome in solving them.
In the case of genocide and human rights abuses abroad, it is not only difficult legally muddy to intervene in a sovereign nation's affairs, but comes at a huge economic and human toll to all involved. Most crucially, there is not a clear track record of success in the cases where intervention has occurred. Often times, it can protract the conflict or destabilize the nation it is occurring in.
We have an obligation to everything we can, but most of the time intervention is not a practical option.