The beauty in the symbolism of the fruit and the fall is that it doesn't require a literal Adam and Eve. The plan is not affected by it. We aren't born into a fallen world because of Adam or Eve. She tasted of the fruit [sin] to learn good from evil. We can't know the difference if we have not tasted the fruit of sin. Coming into the fallen world is part of the plan for us to overcome the natural/carnal/sensual/devilish man. What difference does it make if Adam and Eve were real people?
Well this certainly may work for taking a spiritual view about God and heaven and life. But it poses great problems for Christianity being God's truth to the world and be connection, the LDS Church being the one true church.
But let's just look at Christianity. The whole premise is God created the earth as a paradise and intended his first creations of humans, Adam and Eve, to live in paradise with their offspring forever. But Adam and Eve rebelled, sin and fell from grace and paradise. The messed it up and now sin is in the world, we all sin and we have all been cut off from God cause if you sin, for some odd reason God demands death and blood as the punishment. Now we cannot question this because God is perfectly holy and we are just rotten pieces of clay that he created and can destroy. So, because he loves his imperfect sinful creation he will now send his Son to pay the blood his holy ways demand. All we have to do is accept that Son and His gift, and follow him and we can be made perfect and be with God (return in LDS ideas).
So no Adam, no fall, no need for a literal Savior so who needs Jesus? If by one man Adam comes death and by One Man Christ come eternal life it seems the two are inextricably connected and certainly were in the writers of the New Testament and the theologians that followed.
Now some of this is further complicated by other ideas. Hype Calvinism says God knew all this and planned to save some and damn some right from the start. One then wonders why he put us through it all in that case. In Mormonism Adam and Eve had to fall and we have to be born into a fallen world to experience opposition and be tried in order to test our faithfulness and to develop Christ like attributes. Further Adam is a real character that helped create the world and will return to head up things on the earth before Jesus returns.
Evolution does cause problems for LDS doctrine [whatever that means] but that is always evolving with continuing revelation. ;)
It causes problems for LDS and Christian doctrines unless one becomes a very liberal Christian thinker.