When using the macOS task switcher, when selecting the app with minimized window(s), while the app does become active and displays the Menu bar, but the minimized window(s) are not automatically maximized.
You can make the minimized widow for an app maximize when using the task switcher by pressing and holding the Option key before releasing the Command key. This would maximize the minimized window of the app. It would similar to what would happen when you'd click on the Dock icon of the app.
Here are the steps again:
Invoke the task switcher using the keyboard shortcut Command + Tab.
With the Command key held down, keep pressing the Tab key until you have reached the desired app.
Once the desired app is selected, press and hold the Option key and then release the Command key.
You'd notice that the app window in question is un-minimized (as if you have clicked on the Dock icon for the app).