If you don't tell anyone about your idea, how will you get customers?

Tell everyone about your idea. But you have to silo people's feedback. Do they have enough knowledge to actually tell you if the idea is good or bad? Are they a potential customer? If they are a potential customer and they like it, are they willing to pay for it? If they are a potential customer and don't like it, why not? What would need to change about it for them to pay for it?

Build stuff for the people who will pay you for it and then you'll have a side hustle.