I think you're asking many questions here:
1. How do I finish something?
2. How do I create something other people will find useful?
3. How do I monetize my hobbies?
4. What should I make with Rust?
What answers do you think you need? Maybe you already have the answers. If you wish to do something, do it.
I would suggest only a framework that is essentially to think in prototypes.
1. Focus on quantity, not quality. Make 10-20 things.
2. Think simply. Do some small planning at the outset. Don't expand scope.
3. Release early and often. - Set a schedule, follow it. Release whatever you have when the time is elapsed.
4. Define your goals and measure results in some objective form.
5. After you complete this cycle, find a combination of what you enjoyed and what others are using/enjoying and iterate again.