Yes, we should have done nothing. If the alternative was engaging in a proxy war with pretty obvious political aims.
Why haven't we done something about South Sudan? They've been a failed state with rampant genocide. OH, because we don't have political interests in that state/region. That's why we haven't meaningfully intervened.
I don't know how people can still believe we intervene out of humanitarian concern. Look at all the humanitarian disasters in Asia, Africa, and South America that we just didn't give a shit about.