The very idea is ill-posed and "not even wrong." It is a sort of uncritical and naive secularization of the theological idea of "salvation" which is actually a much more well-posed concept. That's about redemption and saving "souls" and the calculus of sins and rewards. With some care in the analysis and porting, that stuff can be made coherent even if you eliminate the theology and the good/evil dichotomy. It simply turns into the idea of seeking wisdom/self-actualization and ridding your mind of delusions.

But if you do it in a dumb way, you get the idea of "save the world." Even in apparently clear-cut cases like nuclear non-proliferation, it doesn't hang together. You have to get to extremely literal-minded scenarios like asteroids headed for earth to get to coherent instances of "save the world" problems. So if you want to work on an asteroid-busting technology, go right ahead. Anything more complex and you're basically doing really sloppy and shallow secularized theology.

"Change the world," yes. "Save the world," meaningless.