I write for many reasons from catharsis to learning about something to exploring an idea...
The number of stories I've written is much greater than the number of stories I've published, but I don't care. I needed to write that story about sexual harassment long before #MeToo allowed me to talk about it freely. I wrote a funny mummy story because my daughter made a silly joke in the car one day, and I had so much fun with it! My love of other cultures often leads me to write about ethnicities other than my own.
I don't regret any of my file cabinet manuscripts. Telling each story gave me something that I needed at the time. Each one taught me about myself and about the bigger world.
I do have one regret: the time I changed my exciting (to me!!!!!) story idea to something more "high concept" for my agent. It's not that I regret writing the story; I found a way to connect with the new idea. I learned things. The manuscript didn't sell - my agent dumped me before we even reached the submission process. And I rushed into a poor fit relationship with a rebound agent.
As traumatic as that whole mess felt at the moment, all this time later, the only thing that really bothers me is that I still haven't written about my original idea. I still need to write THAT story.
The right idea is the one that is your own.