What have you built that didn’t work and what did you learn from it?

I’ve been thinking about all the products that never really took off - not because they were bad ideas, but because timing or execution wasn’t there.

I’ll start: I built a niche job-posting platform over 10 years ago, way before similar ones became popular. Had no marketing skills and budget back then, so it went nowhere. Good site though, I added it to CV and found very good job