I'll wade in briefly, but I don't have time this evening to produce a scholarly tome on the subject.
Cultures, in my educated opinion, originally were bio-regional in origin. With the basis of similar foods and languages and from ways of learning to get along on the land and speaking and eating, religions arose. Autochthonous religions, based on the place and how to live on it. As some of these grew and became disconnected from the land, they became instead instruments of business, of industry, and of government, they became juggernauts that spread and shifted and became something more than cultures. They became commingled into everything from petty duchys to nations.
Many of the religions that remained close to the land where they rose. They are still associated with small populations and had at their hearts truly beficial human and eco-friendly beliefs. Those are the ones that today are appropriated and mimicked (and even then, the appropriation is largely imperfect, leading to the "Pollyanna" claim above). These are resisting being sucked in by larger industrial religions, and by nations in which many religions exist, with a few dominant. Others religious factions within the nation states are fighting to free themselves.
So we live in a political world that is all mixed up and disconnected from it's origins. I doubt you can sort it out to the point that you can uphold the claim it's a naive notion that all cultures are equally valuable to humanity stick. Because it begs the question "which ones are less valuable, and what do you propose to do about it?" There are thuggish factions everywhere. I'm not denying that for a moment. Within their own cultures they are often considered pariahs. But it is with extreme hubris that we begin to weigh the value of the cultures of others.