Many people call the medieval age a dark age. Why would they call it that way?

Native speaker’s answer
Rebecca
After the decline and eventual fall of the Western Roman Empire, the rate of literacy in Western Europe fell dramatically. People no longer had access to the same resources and infrastructure as under the Roman Empire, so they had to spend most of their time farming to survive. Fewer people could read and write, so the progress of philosophy, science and art slowed down dramatically. The term "Dark Ages" is less commonly used now, since more historians recognize that there was still a lot of progress made. Even though fewer people had access to knowledge and education, this wasn't the case everywhere.