Well, for one, religion has changed, as well as the practice of those religions. Christianity and Islam, the world's largest religions, did not exist/rise to prevalence until just prior to the Middle Ages. The changing nature and expression of religion would certainly cause differences in art expression. Certain religions were also oppressed through the eras you've mentioned, and oppression and fear are powerful emotions that would also influence art. There are a million different factors that go into this, but I hoped this helped a little.
Answer: Art has often centered itself around societal belief systems and the aesthetic of the times. Taking on a eurocentric point of view in this answer; in medieval ages, societies ran on superstition and the power of religious authorities, and the art of the time reflected that as the majority of art created were of deities. After the Age of Enlightenment and the romantic movement, rationalism and realism swept the artistic world. Here, religious powers were represented less as artists and writers began focusing more and more on the tangible and the transcription of real life. In the Post-Modern era, where we are now, religious works don't often come from a place of worship anymore. They have become more of a platform for debate, discussion, and acceptance conveyed through visual work.
In Africa not all places are able to enforce laws or provide basic goods and services to its citizens because of high crime rates, political corruption, ect.
