My long experience in a start-up environment as well as acting as a pseudo division of my clients creative teams' exposed me to many different processes and methodologies of getting from a vision to production.
What I have learned is: Every great product or experience has an equally great and passionate team behind them. The communication, trust, and effort that are required can be directly connected to the success of a product. Ideating with stakeholders, engineers, and designers is essential a long with having a spirit of always asking: Why?
Agile methods; if done correctly, should always press us closer to that answer and merely not be a process that is done because "that is how everyone does it".
Ideate. Learn Fast. Iterate. Ship.