Understanding how political systems operate and how they’re structured is firmly within the capabilities of political science.
Understanding broad political philosophies can help you better understand any individual policy, and political science can help you understand the types of outcomes a policy is _likely_ to achieve or fail to achieve.
But as a science, it’s not robust enough to make especially reliable predictions, and while understanding mainstream or even fringe political philosophies can be valuable, it is beyond the remit of science to tell you what the “correct” expectations are to have of government and society in general. Because that entirely depends on personal values.
Understanding the structure of government is largely a matter of understanding law and formal procedure. This understanding can be validated by decisions that courts make when resolving controversies relating to that structure.
Validating an understanding of political philosophy cannot be done scientifically, which is the same for all areas of philosophy.
Validating an understanding of the outcomes produced by certain kinds of policy can be approached somewhat scientifically, but you’re never going to derive reliable predictions, or conclusions that are widely agreed upon. Which is the same issue that all scientific research of human behavior encounters, in this case further complicated by the fact that the domain is the entirety of human civilization.
In what sense does it help you understand? Is it just that you can tell a story(non-predictive) about what has happened?