GOD did not make a mistake we did. We were made in GOD's image and likeness. We were not made to sin. This world is not as GOD intended. This world is the result of our choosing not GOD's. Because of our choices GOD had a plan in motion from the start. But GOD's intention from the beginning for mankind was to live in harmony in HIM; in love. We chose this through our own devising not GOD. This world and it's system is a result of sin not GOD's plan. HE is just working with it.
1. It makes God to be just a reactive God, not a creator. Its like a chemicist who do something and wonders what will be the outcome. It makes God not knowing all and his actions to be random, experimental.
2. It makes no sense logically. If God is creator of everything what exists, He is the one setting rules and laws leading to everything that happens. So how can something that was not planned happen?