So in future, build a landing page, start shipping it around and see if you can get some early potential customers interested.

Or, choose a small thing you can build in a few weekends, get it built and try shipping it.

If you get no traction, you learned something. If you do, you can now invest more.

This is the whole idea behind lean startups: don’t assume tou have a winner or a stinker, go find out and adapt based on feedback.