This part in Church history not only recalls the point when the one Catholic church became Roman Catholic by focusing more on the bishop of Rome as its leader. Now we see the beginning of contextualization which led to liturgy, which I love, and veneration of beings other than the Triune God, which I despise. This will be a more negative post.
More barbarians came into town, and the people wanted to convert them to Christianity. They took the seeker sensitive route and tried to gradually slide them into monotheistic worship by saying they could still simply talk to dead heroes and people in the Bible. This created a chaos. This also caused a rift between clergy and laity. The elders became priests and developed a sacerdotal system of worship. The same system that ended with the fall of the Jerusalem Temple because we did not need it anymore; Jesus is forever our perfect high priest. All believers have direct access to God through Jesus. But they developed a priest system again with some having more access to God than others.
Back to the saints, the church also started to develop the doctrines about Mary that they are known for: her perpetual virginity and her sinless life (not dogma till 1854). They decided that we can pray to her because Jesus would like to hear from his mother. This is when the "Mother of God" title became known, at the time of the Nestorian controversy.
All the same, Mary did give birth to Christ. And he happens to be God the Son. And she was a virgin at the time. However, the whole Church is the new Eve to Christ's Adam as we all bear Christ in our souls, his blood in our bodies, and are all his Bride. Mary just obeyed the Lord. We can too. Any good attributed to her is the credit of God alone and she would hate the attention she gets today.
This was the beginning of many of their rituals and customs, some good, some not. All churches do this, not just the Roman Catholics, but they made it popular, so they get the attention.