Here’s an example for you...
Christ said He “is the door.”
Will you argue the plain meaning of the words is the meaning of the statement?
If not, what is the meaning? How do you know?
If you say yes, please explain why you believe Christ is a literal door.
Best.
The plain meaning of that passage is that Christ is in a certain sense like a door to the Father. That we are dealing with a metaphor is clear from context. For example, He uses a sequence of images: He is also a vine, and a shepherd.
When Christ says “This bread is my body” He is not teaching a parable, not explaining the metaphor, and in fact spends half the chapter 6 in John’s gospel to reinforce the literal meaning. So He means the Eucharist literally.
When St. James writes “you are not saved by faith alone” there is no possible allegorical meaning at all. Again, half the chapter is spent on that very subject. It is a doctrinal teaching, not some figure of speech.