Humans make mistakes and either learn from them and progress or not learn so falter and fall repeatedly. By learning what went wrong in past history of Islam we understand how, when and where the pure teachings of the Qur'an became diluted, covered with falsehood. If it makes us change from our indoctrinated beliefs, then we will benefit.
The Qur'an is for all time and needs understanding from itself, but we also require new thoughts for changing circumstances so long as they do not go against any universal principle of the Qur'an.
We do not chain ourselves to the Qur'an in any deaf,dumb and blind manner but use it to unchain and set us free.