Hi, Tara,
Thanks for stopping by the Apple Support Communities. If we understand, you would like the option to minimize an entire app, not just the active window. We are happy to get you on a path to get your feedback heard!
Currently, what you are experiencing is expected behavior in that utilizing the minimize button on your active window minimizes just that window, and not the whole app. As an alternative, you can press Command+Tab to quickly switch between apps and we encourage you to provide Apple with your suggestion for additional minimize options here: Feedback - macOS - Apple.
Get more information on managing your windows here: Manage windows on Mac - Apple Support
Best!