The Articles of Confederation weren't an effective form of government for the former American colonies of Great Britain. That's why they were replaced with the Constitution less than a decade after they were finally ratified, at the end of the War of Independence.
The most important reasons why the Articles weren't effective were that the central government wasn't strong enough to compel the new States to pay taxes regularly, and the States refused to support a standing army of any size. This meant that the government was hamstrung by lack of revenue and incoherent domestic policy, and foreign and military affairs were plagued by suspicion of the central government by the States, and by their suspicion of each other.
The Articles did have some positive qualities, though. They provided a framework in which the newly-independent colonies could organize themselves for short-term collective security after the War. During the War, the Continental Congress did this, but that wasn't a long-term option for governing a new country. Its leaders knew this, and drafted the Articles. The Articles also gave the Founding Fathers a point of reference, something to start with when creating a new form of government. Having detached themselves from the British monarchy, and unable to craft an entire political system out of anarchic chaos, they needed a baseline set of principles on which to argue about the new system of government. The Articles gave them this, though they weren't written for that purpose.