Teams thrive on the tension created from diverse points of view. To get those varied opinions in your group, start by finding the biggest critics of the challenge you’re working on.
These may be people who think the project is a waste of resources or who advocated for it to go in another direction. Set up informal meetings with these harsh critics. Then hear them out. Let them tell you exactly what they think. Don’t get defensive. Then, and this is the hard part, ask your critics to join your team. In the worst-case scenario, they’ll say no, but you’ll likely have learned about alternative ways to solve the problem. In the best-case scenario, at least one of them will agree to join forces with you. You will have turned an ardent critic into a passionate supporter and added much needed diversity to your team.