>So, how is it you propose it’s a modern invention? That is, what timeframe constitutes “modern”? Even 300s is considered early Christian history.
I consider it "modern" because it was invented when the Christian church was already established to address controversies with existing doctrine (the divinity of Jesus, the nature of the Holy Spirit, etc.) It wasn't a concept that would have been recognized by Jesus or the disciples, or any Christian for centuries. It isn't in any of the Gospels except as language that was later ex post facto interpreted as referring to the Trinity.
>Likewise, from the early Church onward, Christians were careful to distinguish reverence for and intercessory invocation of martyrs, saints, and angels, who are all just creatures, from worship of God.
Christians can justify it however they like, to an outsider there is little if any difference between praying to a saint or angel in their specific domain and praying to a household god of that domain. In some cases these beings are direct reinterpretations of pagan deities. You have families and people "protected" by specific saints or angels, and using artifacts and symbols to summon the power of those beings which outside of the Christian context would be considered occult practice.
I called these things pseudo-polytheistic because they seem to draw from similar cultural impulses and have similar features but exist within a contrary theological context.