Adam knew good because he knew God. Adam and Eve had access to all wisdom. God did not want them or us to be ignorant.
We were supposed to trust Him as our ultimate fulfilling source of good and wisdom. Humanity, however, pursued a weaker, counterfeit wisdom.
Instead of joy and fulfillment, Adam and Eve received shame. They had never known shame before. They had no way to, for they had the unashamed innocence of God.
Now, shame, deception, and separation entered into humanity's story. The picture of unified tranquility and peace in Eden was torn apart.
Adam and Eve could no longer live in the direct presence of God. They had to leave the garden God had lovingly placed them. Sin had brought blame between Adam, Eve, creation, and God. Now there would be separation.
They did not leave hopelessly. There was a promise. God would strike the snake through the 'Son.' God seals this promise with the making and giving of clothes to cover the shame of nakedness.
Blood must be spilled to cover sin and shame. It would be God who would later spill His Son's blood to do just that. The rest of Genesis and the Bible tell the wonderful anticipation of the Son who will crush the curse of sin and shame.