To get the best ideas from people, remove all the negative consequences of their proposal. Remove all possible negative personal, social and professional consequences.
Make the ideation process anonymous and have only positive reviews.
When trying to find the best idea or solution on a set, there is literally no reason to criticize. The only thing that counts is the best solution, not the gravity of the other solutions. Since this is a comparison, all that is negative about A can simply be said positive about B. Just use positive points or a scale.
Ask the team members to submit their ideas. You present the ideas to the team without the name of their creator. This avoids social anxiety in the face of failure for the creator and prevents personal emotions from affecting the opinions.
Team members only review or evaluate ideas positively. In this way, people hear compliments and what works with their ideas without being criticized. The team is forced to focus on what works when considering ideas. The owner of the winning solution can be named or you can even leave this anonymously anonymous also on behalf of the team.