The title is a bit overstated. A more tempered, and personal, version would be, "I find it very difficult to believe those who say they take all of the creation account in Genesis literally."
Why do I say that? There are metaphors in the account that cannot be taken literally. And, if they are taken literally, the interpreter runs the risk of missing the true intent of the metaphor. I'll give a couple examples.
1) In Genesis 1, God separates light from darkness. God calls one Day and the other Night. This is the 1st day. And yet, the luminaries of the sky (Sun, moon, and stars) have yet to be created. Now, I ask, "What is a literal day?" A literal day is, at the very least, a twenty four hour period in which the earth rotates on its axis-the sun being that which determines light or dark. One cannot form a literal concept of a day in regards to the first day of creation. In other words, a metaphor has creeped in somewhere. Someone might attempt to explain the separation of light from darkness by saying, "On the first day, God separated right from wrong, good from evil, good angels from fallen angels." Fine. Whatever. I have no problem someone interpreting the metaphor. That's what we are supposed to do with metaphors. But, let's at least be honest and admit it's a metaphor.
2) In Genesis 2:17 we are told of the "tree of the knowledge of good and evil." I ask myself, "What kind of tree is that? How do I form a literal conception of that kind of tree?" I challenge anyone reading my words to try, at this moment, to form a literal conception in their minds of such a tree. I contend, without having to try really hard to do so, one cannot form such a conception. Why? Because it is a metaphor. What does that fruit look like in your mind?
Here is the important part. Even if someone were able to take all of the creation account in Genesis literally, it would do them no good. What matters is not affirming its historical reliability. What matters is grasping the spiritual truths being communicated in the account, e.g. God exists, God is Creator, creation is not God, creation is good, humanity is created in the divine image, sin is a killer, humanity is in need of redemption, a promise of redemption has been made, etc.
Believing that something is historically true does not change anything. I believe Billie Holiday is the greatest jazz singer of all time, that doesn't somehow change my life. Arguments over taking the creation account in Genesis literally miss the point (including the argument I am now making). The point is the truths being communicated via the account. And, happily for those of us who accept the account, science can't communicate those truths to us, only the account in Genesis can do that.
Does what I am saying make sense?