What important powers did the national government lack under the Articles of Confederation and why was it created that way in the first place?

Important governmental powers not held by the Articles of
Confederation Governmnet: A good book for you to read is The Articles of
Confederation by Merrill Jensen.  Is is not too long.  It has been years
since I read it, so my answer will not be so good as you might get from others, but here
goes.

Given that the USA was governed by the Articles of
Confederation throughout the long War of American Independence, and given that the USA
won its war, there may have been no essential powers lacking, but your question was
about important, not essential, powers.  Under the Articles, the Confederation
government could only ask the states for money; it could not take taxes directly from
the people.  Being able to directly tax the people for money to finance a defense
establishment and to finance international diplomacy, permits a better army and navy and
more respect in international relations.  Direct taxation has its drawbacks.  One
example is "The Road to Nowhere" built in my county by the U.S. Forest Service.  The
road goes for several miles through the mountains; it is a wide 2-lane paved road; it
ends at a 1-lane, county, dirt road.  If the dirt road is good enough for residents to
drive on every day, why is "The Road to NoWhere" necessary for hauling logs only part of
the year?  Answer: It isn't necessary, but  government bureaucrats like to spend money;
it makes them feel important and keeps them busy.  Direct taxation makes it too easy for
Congress to spend money all over USA on pork-barrel projects.  Perhaps the government
should be allowed to lay direct taxes only for defense and diplomacy; perhaps all other
federal monies should have to come from requisitions on the states, as it was under the
Articles.

Another problem under the Articles was that many,
maybe all, states had regulations that restricted trade.  For example, if a state had a
hat-making industry, it might prohibit the importation of hats from other states.  This
prevented consumers from purchasing the best hats for their needs; it prevented the best
hat makers from making the profit that they deserved; it permitted the local hat makers
to charge higher prices than they deserved, and to sell poor quality hats.  Some amount
of control of interstate commerce was needed to stop these sorts of abuses.  The
Articles gave the Confederation government no control over interstate commerce.  Under
the present Constitution, the federal government controls interstate commerce, and there
have been abuses of that power by both government and special interests.  Some amount of
control is better than no control; too much power to control may be worse than no
control.

The reason the Articles did not give the
Confederation government all of the powers that most governments have, is that the
people setting it up saw the state governments as the legitimate governments and the
Confederation government as only a means to do together the few things that the state
governments could not do individually.  The people who wrote the Articles had just
seceeded from their home government located in London, because it had tried to use its
power to lay taxes and regulate commerce in ways that many Americans believed to be
unjust.  They did not want to give these same powers to the government that replaced the
one against which they were rebelling.