@SarahGen-- I agree with you. It's easier for a company to change its mission statement than to change its strategies though. Almost always, the issue is a too narrow mission statement. So making it larger and more encompassing will probably solve the problem.
I think the most important aspect of a company strategy is that it should have foresight. The company must have an idea of where it ones to be after a decade or two decades and the strategies must be effective enough to get the company there.