Collaborative decision-making seems like a great ideal, but making a team-wide decision is so much easier said than done.
Most of the time, teams struggle to make decisions not because of poor communication, but because of the decision-making process itself.
Each team member has their own goal(s), influenced by their own projects, their own constituents in the organization, and/or external clients. The action steps that they recommend will inevitably be influenced by those factors.
To improve your team’s decision-making process, clearly define the goal and outcome(s) that must be achieved. When everyone aligned on accomplishing the same results, it will be easier for them to set aside their personal projects and start to agree on strategies.