As you indicate, there were many ways in which the Articles of Confederation set up a national government that was too weak. Two of the major limitations on the national government were that it A) had no executive branch and B) did not have the power to tax the people.
The lack of an executive branch meant that the national government could do little or nothing to carry out the laws that it made. This meant that it would have to rely on states to enforce the laws and the states could simply ignore laws if they did not like them.
The inability to tax meant that there was no way that the government could reliably raise revenue to fund any government operations (even essential ones such as defense). The national government had to ask the states for money and the states could easily refuse.
These were two of the major ways in which the national government was limited under the Articles of Confederation.