I find that when people talk generally about "changing the world" that they are thinking about doing something grand and majestic but we all have the capacity to "change the world" in our own small way which may not ever be recognized (being well known for something doesn't necessarily make it a better accomplishment).
For example, suppose you are a case worker and help at-risk youth complete school and go to college. Perhaps you live in relative obscurity but someone you help is saved from making bad choices and goes on to do something big and exciting. Did you change the world? I would argue yes, but maybe not in the way you had first imagined.
Like @Sandra says, if you are doing things in your life that are meaningful and fuel your passions, who is to say you aren't making the world a better place simply thru your influence on those around you? The opposite, a world where everyone is completely self-centered and has no passion beyond advancing their own popularity doesn't seem very great either.