Carl Trueman has a very helpful post connecting the theological dots related to the historicity of Adam and to the way in which Evangelicals read the opening chapters of Genesis. His point is that biblical doctrine is always connected and interrelated with itself, with certain basic doctrines supporting other later developments and fulfillments.
We can go further, perhaps, and ask the basic question as to what it is that salvation in Christ, or even “religion,” is supposed to accomplish. If it is only a coherent and meaningful self-narrative, then history is obviously less important. But if that narrative is expected to actually affect the world outside one’s mind, well, then the situation becomes more complicated.