If you want to know what "the Dark Ages" are like, move to a nation which does not have a Christian heritage.
Do not move back in time to what atheists and secularists call "the Dark Ages."
By that phrase they mean "Christendom" in its infancy.
They mean the centuries following the fall of the Roman Empire, which secularists think of as some kind of "Enlightenment" paradise.
What a joke.
If you want to know what "The Dark Ages" were really like, read Tom Wood's book How The Catholic Church Created Western Civilization. Watch this video series.
If you want to know what the triumph of secularism would look like, review the world of Greco-Roman paganism.
Gary North writes:you want to know more about the worldview of classical Greece. What did they believe in? What were the foundations of classical Greek civilization? I offer you this list.
1. Pederasty. This is the homosexual union of an older married man with a teenage boy. The men often met the boys on their way to the gymnasium, the building in which the boys danced and played sports naked. The men then became the boys' lovers and teachers.
2. Demonism. The Greeks were polytheistic. Greek family life rested on a system of sacrifice to demons that masqueraded as the spirits of dead male relatives. So did clan life, which became political life. These demons also presented themselves as underground gods and spirits, who demanded sacrifices and special rituals to keep from destroying people. On this point, see the works of the early 20th century archaeologist-historian, Jane Ellen Harrison. This never gets into the textbooks, although specialists are well aware of it.
3. Warfare. At the center of the literature of classical Greece was Homer's poem, The Iliad. It is the story of how Achilles' resentment against King Agamemnon raged because the king took his kidnapped concubine for himself. All the other men had concubines for the ten years they were at war. But no children are mentioned by Homer. Now that's real Greek mythology! Their wives stayed home and kept the ritual home fires burning -- to placate the family's departed male spirits. Athens destroyed itself in Pericles' needless imperial war against Sparta. Then the Macedonians conquered war-ravaged Greece. But the textbooks praise Pericles as a pillar of wisdom, reprinting Thucydides' posthumous version of Pericles' suicidal imperial oration.
4. Slavery. At least one-third of Athens was enslaved. The figure was as high in Sparta. Every household owned a slave. This provided leisure for their owners, who despised physical labor as beneath them -- servile. Slavery was a universal institution in Greece.
5. Autonomy. Greek philosophy was based on the ideal of man's mind as completely sovereign -- no personal God allowed. Well, not quite. Socrates claimed he was given guidance in his thinking by a demon (daimon). But rationalistic scholars, beginning with Plato, have always downplayed this. They have sometimes said this was just hyperbolic literary language. Socrates could not really have believed in a demon. After all, they don't.
6. Welfare State. At least one-third of all male Athenians were on the government's payroll in the time of Pericles.
7. Human Sacrifice. This was a basic theme in Greek literature. It was part of Athenian religious liturgy. There was no widespread movement to decry the earlier practice. The great expert here was Lord Acton, who wrote a long-ignored essay, "Human Sacrifice," in 1864. It is online here. It is included in Volume 3 of Selected Writings of Lord Acton, published by the Liberty Fund. From the day he published it in order to refute the great historian Macaulay, historians have refused to incorporate it in their narratives. It is way too embarrassing.
8. Cyclical View of Time. The Greeks did not believe in long-term progress or a final judgment -- just endless cycles forever: rise and fall, rise and fall. According to the historian of science, Stanley Jaki, this was why the Greeks never developed science, only technologies.
9. Female Inferiority. Wives were only for procreation. They could not be citizens. They had no legal rights. A man needed a male heir to perform the ritual sacrifices to feed him after he died. Women had no political influence except as prophetesses and mistresses.
You would not want to live in ancient Greece or Rome. See also this and this. You would say they were "uncivilized." Bishop Augustine was saddened by the fall of Rome, but Salvian the Presbyter understood that real civilization is based on Christian morality: Salvian rejoiced at the fall of the Roman Empire.
Read more about the depraved Roman Empire.
It is Christianity, not atheism, that brings enlightenment, peace, and prosperity. In short, civilization.