These critics overestimate the impact of Ebola. Even with this current weak system, the recent Ebola outbreak has had a death toll of 7,645 as of Dec 23. A million people die every year from Malaria, and some (optimistic) estimates say that the Gates' efforts could save 5 million lives.
This seems like a classic example of our tendency to overestimate the importance of singular, cataclysmic impacts, as opposed to predictable, systemic ones.