Marijuana exists because God cursed the ground after people sinned. A judge can't just change the laws to exempt someone from a legal punishment because the law doesn't work that way.
Christianity is historical. It has a timeless message. The Bible does relate to us today. All the authors wrote under the inspiration of the Holy Spirit. He doesn't make mistakes, and He is always timely and eternal, It was written by 66 different authors, all with the same message. What are the chances of that? They all had the same themes of redemption, seeking God, making God a part of your life, the Messiah. The Bible applies to people in all cultures, all generations, all races, and all situations, circumstances, and social stratas. The Bible is about real people, places, and things-archaeologists are revealing more and more about the accuracy of the Bible. The Bible is the most studied and researched book in the history of mankind, and what it says has been shown to be true again and again. The commandments of the Bible are the absolutes of God-His opinions on sin, judgement, righteousness, obedience, forgiveness, and holiness have not changed and will not change.
Regarding the claims of the Bible being unsubstantiated and some Bible stories being myths, it's possible stories like Adam and Eve are allegories. I don't have a fully formed opinion on whether Genesis is an allegory because it's not important. That doesn't disprove the Bible. Whether Genesis is an allegory doesn't detract from the message. When you begin to discount or dismiss the Word of God, you'll find that there's no end to discounting it or dismissing its value. On what basis can you say that some of the Bible is true but other parts aren't? On what basis can you say that you believe some of the miracles but not all of the miracles? On what basis can you say that the love of God is good to believe but the justice and righteousness of God aren't good to believe?