Can someone please tell me am I right or no, about Vapor barriers – GreenBuildingAdvisor

Hello everyone, recently I read about Vapor retarders in ventilated attic, ventilated crawlspace, ventilated cathedral roof, and I understand that in cold climate I can place the Vapor barrier near the drywall (under insulation) in all these areas. And then I found on the internet that in hot climates it is not recommended and not good to put Vapor barriers anywhere in ventilated attic, ventilated crawlspace, ventilated cathedral roof, and I should focus on ventilation instead. Is that true? Does anyone know? I appreciate the help