If Adam and Eve (by inference) are clearly allegorical, then so too is the fall..and salvation becomes a meaningless concept. You can't have one without the other, but if believing this logical contradiction helps you sleep better at night, then hey, go for it, enjoy it while you can. There is no better sleep than a fool and his dreams.
So if we were to take your argument to the logical conclusion, all of Jesus' parables must not reveal pertinent truths either.
Just because two people named Adam and Eve didn't exist doesn't make the theological/ moral basis of their story any less true. The idea behind Adam and Eve is that we, as humans, are imperfect and are going to sin because of that imperfection. I don't need Adam and Eve to be real people in order to understand that.