Google sites alternative use cases revolve almost completely around student creativity. There aren’t many ways to use it in a way that is different from its natural order, but the fact that most aren’t using it in that creative way means you could see them as alternatives.
The key with sites is that it’s all in Drive. It allows sharing and collaboration to be done easily, and it makes it easy for any student to start a site. It also means you don’t necessarily have to even publish them. You could just shrew them through the Drive sharing function.
Sites are also incredibly easy to use. Students just need to drag and drop content into it, and it is easy to add some of the other Google tools like docs, sheets, slides, and forms.
Some ideas for Sites: