I'm sure you can think of ones I haven't. Each of the above challenges can block our pleasure in reading or viewing. The work assumes an audience of some kind of background, knowledge, and interest. It also delves into issues that go beyond the concerns of a particular time and place. No one work can say everything about a subject, so something must be assumed.
Great works tend to appeal to 'educated' audiences on some levels and to all humanity on others.
As a quality of the audience , knowledge means that the viewers or readers have background information and experience that them access to many levels of the work. We can learn. We can become educated. We don't really have to, I suppose. However, in my experience, the longer people live the more they seem to be dissatisfied with their first choices in life.