The speech isn't telling us what it's like to be in war or deal with cancer. It's telling us there's a difference between reading something and experiencing something. Whether it uses the real life experiences of Robin Williams or the fictional ones of his character is beside the point.
exactly this. the point is the message, that you need to experience things to really understand them. that is true regardless of how the message is delivered or who delivers it. if robin williams actually experienced all these things doesn't matter, because even if he did, matt damon listening to that would not be different from him reading about it unless matt also experienced those things.
life experience matters, and robin williams certainly had life experience at that point. i am in my 50s and i am only beginning to be able to translate my own life experience into some kind of wisdom that maybe can be shared.