Musk might be considered a counter-example here. In fact, part of his mission is literally to "make a better battery". Of course in depends on how much you buy into his mythology. Certainly he could have comfortably retired after Paypal though. (Rather than moving on to run two groundbreaking companies - something I'm not sure how one person manages to successfully do.)
Musk clearly finds what he does meaningful to himself and is not doing something he does not enjoy simply for the greater good of humanity.
Notch did not enjoy being part of something so large. I find it odd to belittle him for choosing the path of doing small things, since that is where something as impactful as Minecraft was created in the first place.
I'd say Minecraft was grown in spite of the way Notch works. The way he works has been the bane of a lot of modders, who are (arguably) the reason his game is so successful.
> In my opinion the important part is that you are doing something meaningful to you as an individual. [...] ...the world would be so much better off if we just had everyone doing this.
You can't separate yourself from humanity as a whole. That's like saying your liver should do something meaningful for itself as an organ, and if it ends up helping your body, all the better. We don't work individually. Humans require other humans, and all of our motivations and desires are influenced by this requirement.
Notch may not have begun Minecraft with the larger gaming community in mind, but he certainly continued development in some small part because of it.
But of course this is all just a personal opinion and highly subjective.
Notch however, clearly did not enjoy working on something with so much publicity whether it benefited humanity or not. I don't think we should belittle him for that.
Not knowing how to do something doesn't stop me from trying to do it. Why does it stop you?
What you are suggesting is impossible. No one, not even Steve Jobs sits down and says "My life mission is to benefit humanity". This is because we really do not know which efforts will have the largest impact on humanity. You could waste a lifetime trying to make a better battery - but it might never happen.
Or you could hack around on a game and watch it explode and impact millions of lives around the world.
In my opinion the important part is that you are doing something meaningful to you as an individual. If it ends up exploding and benefiting humanity all the better. But the world would be so much better off if we just had everyone doing this.