To determine the "MOST IMPORTANT PERSON ALIVE" we must follow a certain criteria to do so:
(This is what I think some of the criteria)
1. If he/she dies, will the world be shaken by his/her death?
2. Is he/she in a state where all of his/her movements are under close surveillance of different agencies in every nations?
3. Can he/she influence more than 2/3 of the world's population?
4. Will his/her death cause war, or any event with same degree?
And I don't think any of the list has the quality to have 3/4 of whats in the list.
I agree with you, truth is nobody is indespensable and as important as we think they are. I don't think there is anyone that has super general importance worldwide that his or her death can cause a general outrage that will force persons to go against their normal activities.
Also the names of people on that list have different importance to different persons in different locations, that is something to know as well.