This feels right, but let me refine my understanding. First, the reason for maintaining a strong ego is that it's the lifeline of the team's direction. The person steering the ship must have a clear vision and be ahead of the market, ahead of anyone else on the team. Second, the product itself can't have its own ego because, ultimately, the product is meant to be used by people. Your ego must be built on the foundation of who it's for and why, not just on your own aesthetic preferences.