I'm an engineer too bro.. I understand your frustration. Sometimes you just do as much analysis and design of the product as you can, determine a cut off point to stop the effort and put the product out to market, praying to whatever deity you embrace that your ideas were good and the product works.

This is done with the understanding that all of the factors that determine if a product is good are not in your control...

Sometimes it requires and educated "leap of faith"....