At one point in time, people generally understood how religious metaphors functioned - but then the protestants fucked everything up by printing the bible in the common languages, and suddenly every one of the faith's biggest grifters decided that they knew better than the priests who'd spent their entire life studying it all. The understanding of the bible as a metaphor is still alive in some circles, but in the modern culture you don't even need a grifter to tell you their interpretation anymore because the modern faithful almost all just come to whatever conclusions they like based on whatever fragments of religious education they get as kids. That's why you have self-professed Christians who believe in reincarnation and karma and crystals and shit - they're just grabbing whatever they've heard of that they like.

And it turns out that the people who are most likely to attend mass every week (which by the way is a relatively modern phenomenon - even medieval peasants generally only attended mass once a year) are also the ones most likely to assume that everything in the book was intended by its original authors to be taken literally even though those who've studied it have also read contemporaneous sources saying the opposite.

IMO this all stems from the material condition of the Church being pretty irrelevant politically. At one point in time there was a superstructure to force everyone's beliefs to conform more or less to a certain dogma, but capitalism has rended all of that apart.