The world is full of projects
Do not expect contributors and team members to flock around your awesome idea. In fact, if you just deliver decently good stuff, chances are you may remain relatively alone in the project. Work to aid people to get into the project and ease every step, but do not expect them to come.
Your Open Source project competes with all other projects for the time and skill of contributors, as there is only a finite number of contributors out there.
Those possible contributors have a finite amount of time to spend on Open Source, and their time is also itself shared and competes for attention with other services such as video streaming, social media and computer games.
A related question is how you reach out in this world already so full of existing projects. How do you make people aware of your excellent project? Both users and developers.
The difficult truth is that this is not an Open Source problem. How do you reach out to anyone about anything? It is a generic marketing challenge.
When I do it, I start out by telling my friends to get them hooked on it or at least make them try it out. If they like it, chances are they will help spread the word. If they do not like it, I can use their feedback to improve. I also tweet and blog about it, to reach my extended friend circles as well.
Then I continue to iterate and improve the project and hope that some of the steps above eventually work.