C1 is an advanced level in the CEFR language classification system. Of course, reaching C1 through the testing and progression through the course and quizzes here is not the same as being able to exceed the standard required for formal certification as C1 proficient. Nonetheless, passé simple is a major component of much classic French literature, and also of many children’s tales and nursery rhymes, there are still standard expressions used in ‘everyday’ language in passé simple, and it can be found in higher level modern journalism etc It is much less used in modern literature than previously but is important to be able to recognise. Given the overall structure and purpose of this program, I think it is reasonably, but not excessively, covered. You could choose to just skip it, and refer to it only when the need arises from reading etc 

I agree that practicing phrases is time well spent. You don't have to rely just on kwizzes; there are writing, reading, and listening exercises available at all levels, which may actually be even better suited for this than kwizzes.

Passé simple is something you will encounter frequently when you read French books or even magazine articles. At level C1, you should definitely be able to know how to use it, even though you won't be resorting to passé simple as a tourist asking for directions.