I think the only thing that any Christians "scoff" at is the goofy notion that we should limit ourselves *exclusively* to the book of Genesis when attempting to understand the universe that we live in, and bury one's head in the sand with respect to other scientific fields of study.
It's fine to have faith that God created the heavens and the Earth, but that still doesn't tell us *when* that occurred. Most Christians look to other fields of study to figure out the when part, and to understand how nature works.
The problem with excluding every external reference point in the universe when looking to questions about our origin is that it requires one to "assume" that they, and they alone have power to "properly subjectively interpret" a couple of a passages from a single book, and they get themselves stuck in a circular feedback loop without a way out of it.
The Holy Spirit has never spoken to me and claimed "Hey Michael, the Earth is only 6K years old and you're personally required to interpret every word of Genesis literally, or else!". Give me a break.
If you consider Genesis 1-11 allegorical, what foundation do you as a Christian turn to (before Jesus came) to understand sin, death, the need for a Savior, the reason for and efficiency of a blood sacrifice, marriage, clothes or the seven day week?
I wrote this to Joshua. The Scripture is crystal clear. The real issue is God's authority versus man's authority. If God wrote this book, it is utterly trustworthy. If we reject pieces of it, it's because we think God is wrong and man is right.
The 6 literal day creation is not a myth.
Exodus 20:11
11 For in six days the Lord made the heavens and the earth, the sea, and all that is in them, and rested the seventh day. Therefore the Lord blessed the Sabbath day and hallowed it.
Genesis 1:1 says, "In the beginning, God created the heavens and the earth." Then the rest of
Genesis 1 goes on to describe the way He did it in six days.
The days are defined very clearly.
Genesis 1:3-5
3 Then God said, “Let there be light”; and there was light. 4 And God saw the light, that it was good; and God divided the light from the darkness. 5 God called the light Day, and the darkness He called Night. So the evening and the morning were the first day.
Also, God created the heavenly bodies on the fourth day. Notice how He discusses seasons and years:
Genesis 1:14-15
14 Then God said, “Let there be lights in the firmament of the heavens to divide the day from the night; and let them be for signs and seasons, and for days and years; 15 and let them be for lights in the firmament of the heavens to give light on the earth”; and it was so.
If the fourth day was an indeterminately long age, what does God mean by seasons and years? Also, since the day is defined as dark and light (just like an ordinary day today), how could the plants created on day three survive the great period of darkness?
There's no Scriptural basis for taking the days of
Genesis 1 any way other than literal days. The Bible just doesn't allow it, no matter what "modern" people like to say.
Also, God declared His creation very good. There was no death. People and animals were vegetarians.
In
Genesis 2:17, God told Adam that if he chose to eat the fruit, he would "surely die." Adam died spiritually the moment he ate. Adam also died physically, but not immediately. An animal died, though--God shed its blood shed so He could make clothes out of its skin to cover Adam's nakedness/shame. The principle of death being the punishment for sin has never changed (
Leviticus 17:11,
Hebrews 9:22), and it is the reason Jesus Christ shed His blood, dying on our behalf to pay for the penalty for our sins. Also, death was a cancer to the creation. Besides affecting Adam's race, animals (sometime after the flood) stopped being vegetarian, the ground grew thorns, etc. The whole creation groans waiting for its redemption in Christ (
Romans 8:19-22). When He reigns on the earth, He will undo these things (
Isaiah 2,
Isaiah 11,
Isaiah 65,
Zechariah 14,
Ezekiel 47, etc.). The animals who now live in fear of being hunted will graze together and be vegetarians again.
Now think about it, if the removal of the curse will bring peace between animals and also man, then doesn't it follow (consistently) that death was never a part of God's perfect creation (although He knew it would occur)? Now, the only reason to accept long ages is to go along with conventional wisdom: evolution over millions of years. But death is the center of evolutionary biology - survival of the fittest. Millions of years of death and struggle, they preach, resulted in the world we see today. Some naturalists will overlook Christians who say, "God used evolution," but the truth is, they know (better than those Christians) that the worldviews are incompatible. God did not call a world created by death "good," and then turn around and blame Adam for what He already used. God is big enough to create things good the first time, and He didn't need millions of years. (The godless rely on millions of years, because it's the only way they can convince themselves it's possible that He doesn't exist.) If death came before sin, God is a liar and our faith is worthless.
Indeed, let God be true but every man a liar... (
Romans 3:4b)
No, I want to believe as many true things and as few false things as possible. The bible does not pass the sniff check, and accusing me of having ulterior motives is weak. 
