EDIT 12-1-18:
This is a question about programmer's ideation in the UX design process. Why was it removed from the UX section?
This is a question about programming design during the ideation phase of UX iteration. Some example articles on the subject:
NNGroup: Ideation in Practice: How Effective UX Teams Generate Ideas
NNGroup: Ideation in Practice: How Effective UX Teams Generate Ideas
Programmers face issues unique to programming in ideation. The question is about those issues.
To get the best ideas out of people, remove all negative consequences of proposing those ideas. Remove all the possible negative personal, social, and professional consequences.
Make the ideation process anonymous and only have positive reviews and ratings.
When trying to find the best idea or solution out of a set, there is literally no reason to critique. The only thing that matters is which is the best solution, not how bad the other solutions are. Since it's comparison, anything negative about A can simply be stated as a positive about B. Simply use positive points or a scale.
Have team members submit their ideas to you. You present the ideas to the team without their creator's name attached. This prevents social anxiety about failing for the creator and prevents personal feelings from affecting reviews.
Team members review or rate ideas in positive ways only. This way people get to hear compliments and what works with their ideas without being critiqued. The team is forced to focus on what works when reviewing ideas. The winning solution's owner can be named or you can even leave that anonymous too in the name of the team.