The correct answer to this open question is the following.
The most significant accomplishment of the AOC was the following.
The Articles of Confederation gave the colonists the possibility to have a form of government that could unite the colonies during the Revolutionary War of Independence against Great Britain. The Articles allowed the support needed to the Continental Army and represented a form of unification of America to present a solid front to the English troops.
Of course, as you know, after the armed conflict, the Articles maintained a weak central government and strong, sovereign states, that were the ones that could collect money.