But there is no greater pleasure than to finish something, deliver it, get users in front of it, and get feedback you never expected from either grumpy or happy users. I think it's way more rewarding to try to work for profit, because while money is nice, profit also means it's so useful someone is ready to give you credit for future work (money) for what you did.

Not a universal experience. I receive little joy in money, beyond the basic needs it relieves. Shutting down a business that cleared $800M profit annul. was the best decision I ever made.

Profit doesn't inherently mean you've made the median experience of individual humans better, and is just as often to effect significant degradation. My biz was slightly on the positive, but I could have pegged an extra zero in profit if I had forgone scruples.

Even if it makes just you happy, it's impactful. You are the person others have to put up with. Making yourself happy improves the world for those around you.

>Even things that were neither novel (academia), profitable (industry), nor impactful (nonprofits).

You classifications are good but it's a bit simplistic. Generally across the spectrum people is looking for breakthrough (e.g. deep learning) and/or game changing (e.g. transformer) contributions regardless if you're in academia, industry, non-profit, government labs, etc. But for pure joy, it can be from any simple creative projects as you've mentioned or it can be giving up seats for the elderly in a crowded metro trains.