The very idea of a religious text is indicative of something that is interpreted from word or oral traditions. And most books of the good ol days were translated from multiple languages. So therefore, if I have an idea or thought, or even poetry, I would not be able to translate it into another language and maintain the same decorum. E.g. Most religions say “find happiness”. However, the meaning of happiness then and now is different. Happiness was more like bliss at that point.
Another issue is the idea that, people would take poetry and stories to be literally physically possible. Which then gives these stories a sense of mythical truth. E.g. Mahabharat’s million starred arrows flying into oblivion. Judging by the very nature of the act, it seems to be physics twisted and turned.
Old books are like old habits. You cant learn from them after 20 years, and so you repeat them again and again, until you think you’ve spotted a pattern of a truth.