How culture gets created and how to change ?

I will explain this through a simple example of how culture gets created in organizations.
The team is conducting a retrospective.  They capture all the good, bad and ugly items on post-its and capture the action items as well. However, the Scrum Master never bothers to follow up with action items.
Team attends the second retrospective and the similar issues crop up again.  Some one nudges the Scrum Master about the pending action from the last retro and you would hear that it is yet to be done.
By the time you are in 3rd or 4th retro, team members would have lost interest in creating action items as they have lost faith in this process. This has lead to creation of a culture that “nothing works in this team” OR “It is a waste of time”
When new members join the team and observes the retro, they would be surprised to see that no one is creating action items. They could potentially blame the team for this.  Even if the new team members try to bring their new ideas, rest of the team would be skeptical and pull them down by saying  “nothing works in this team” don’t stress yourself.  This trend will have domino effect on the entire system.
In retrospect, it is not that the team was un-willing to do anything with action items, it is the leader who silenced them in every instance. People in power, authority, dominant and influential positions play a key role in  creating culture in the organizations.
Good news is, it is possible to change. I see two options in such situations, either get a new leader who could enable in creating a new culture or get a shark in the team, who could stand up and challenge the status-quo
What is your experience in changing the culture ?