Is it really necessary to believe that an ancient creation myth is literally true in order to be a Christian?
or are Christians allowed to believe that some of the Bible stories are just stories?
I'd argue you can't be a Christian and believe in Literal Creationism.
The barest test of being a Christian is acceptance that Jesus Christ is your Lord and Savior. For simplicity's sake, Christ is God. And God is perfect. Perfection is defined as being without flaws. Therefore, God is without flaws. Therefore, Christians must accept that their Lord and Savior is without flaws. Here is why a YEC cannot be a Christian.
Absolutely nothing we see, hear and test in any way supports YEC. From strata showing fossils sorted by time and complexity (not mass or density as per hydrological sorting), billions of year old light, and DNA showing related species, nothing supports YEC.
Now, if God meant YEC to be literal, then God is lying to us every day by pulling the most Epic deception of all time. God created the world according to YEC, but then changed every physical law, removed all evidence and then planted fake evidence to deceive us into believing the world is quite old. That makes God essentially the biggest liar of all time.
Now, if God created the world as we see it, test it and hear it, then God is a liar in the Bible it he wanted us to believe YEC was true.
Either way, God is the most Epic Liar of All Time.
And deception is not a trait of a perfect being. Therefore, you cannot accept Christ, who is perfect, if you believe in a series of events that makes Christ the biggest liar of all time, and therefore not perfect.