Here's another way ancient civilization was different than ours:
Ancient religious tolerance Two fellows are discussing God. One guy says to the other one, "I respect your right to worship God in your way. I hope you'll respect my right to worship Him in His."

That modern joke wouldn't make sense to an ancient, because ancient western culture didn't have a notion of "right doctrine." In a sense they had many Gods but one religion, a fluid polytheistic pantheism.

At the Temple of Jupiter in the center of Rome believers honored not just Jupiter, but Serapis, or Dionysus, or Mithras -- and no one complained.

Initiates in the the mysteries of Dionysus could and did simultaneously belong to the mysteries of Isis -- and the mysteries of Mithras, and the mysteries of Attis.

Visitors wrote about being told two contradictory versions of a God's myth and rites -- at the same temple, on the same visit!

Ancient cultures didn't really know there was such a thing as unique doctrine, so they didn't teach people to care when others disagreed. There were no religious wars, there were no forced conversions.

By the way

So what? So syncretism. Because doctrine didn't matter, ancient religions borrowed and adapted from each other. Associate professors call this "syncretism." A good way to think of it is, "No copyrights, borrow whatever you want." Ancient civilization was a religious melting pot; Gods and myths and rituals spilled from one faith to the next, from one region to the next, mixing to form new faiths. Over and over people built new religions from old parts

After Alexander (in the 300s BC) conquered the Middle East, the Greek Gods were equated with the Middle Eastern Gods -- not just in name, but in myth and ritual. The Greeks borrowed from the Middle East, and built a new religion from old parts.

The Romans conquered the Greeks and -- you know this -- adopted and adapted the Greek religion as their own. The Romans borrowed from the Greeks, and built a new religion from old parts.

Borrowing and rebuilding happened on a local level too. For example Cybele and Attis are famous for having priests, called Galli, who cut off their own testicles as an act of religious devotion. (No kidding!!). But the Goddess Atargatis also had castrated priests, and so did the God Ma. Ancient religion was fluid and adaptive. Over and over, ritual and myth and theology passed between Gods, between local cultures, between faiths. Over and over, new religions were built from old parts.

Another example: Nowadays we associate frenzied, wine-drunk ecstasies with the God Dionysus ("Bacchus" in Rome) -- and we're right. But other Gods were worshiped with similar rituals, including the Thracian Sabazius (beer, instead of wine), and the eastern Corybas (associated with the Goddess Cybele), whose sacred possession is called "Corybantism." Even Isis and Cybele were worshiped with wild dancing. Ancient religion was fluid and adaptive. Over and over, ritual and myth and theology passed between Gods, between local cultures, between faiths. Over and over, new religions were built from old parts.

The ancient Mysteries of Osiris (written record of Osiris dates back to at least 1,800 BC) celebrated a God who died and came back to life, whose rebirth was seen as bringing salvation to believers, whose worship was entered into via an initiation ceremony that included water baptism, and whose worship included a holy meal established by the God. These elements -- a dying Godman, resurrection, salvation, baptism, holy communion -- were built into new religions that developed centuries after Osiris first appeared. The Mysteries of Attis, Eleusis, Dionysus, and Adonis all had them. Ancient religion was fluid and adaptive. Over and over, ritual and myth and theology passed between Gods, between local cultures, between faiths. Over and over, new religions were built from old parts.