i do agree that a good idea is necessary, but our number one priority has always been having a strong team: a team of balanced members where we can learn from one another and trust each other completely. we've committed ourselves before deciding on an idea for a few reasons:
1) we're all united by the passion of creating something that adds value to peoples' lives 2) we've known each other for many years and have similar interests 3) we understand that we have to be flexible, and we may change our idea multiple times before getting it right. it would be unfortunate to form a team revolving around a single idea, only to have the team pivot to an idea that some members did not 'sign up for'
hope that provides some additional insight.