SCRUM as in Agile software development? If done incorrectly, it becomes a major hindrance to all involved especially when sprint planning and daily stand-ups take longer then they should.
Effectively, the designers and producers become the customer and continuously review the product and possibly change the goals if they find that something they thought was good on paper doesn't turn out well when implemented. The opposite could also happen as in something that they thought was minor was implemented and they then found out was good fun, the feature could be expanded.
It also allows them to prioritise more important game aspects early in the project by defining the goals and also predict how much of the game could realistically be done based on the amount of work that is done per sprint in the previous ones.
In terms of creative power, it does very little besides being able to review the product more often and earlier based on what goals have been completed. If something doesn't turn out right, at worse, only a sprints worth of work is wasted. Essentially, it is game development in baby steps towards the goal.
This is just a general overview of the designer's role in game developments from SCRUM in my experience. It may differ with other companies.