Previous educators have rightly drawn attention to The Wealth of Nations as a critique of mercantilism, the dominant economic system at that time. For Smith, mercantilism wasn't just economically inefficient, it represented a failure to understand human wants and needs, which he felt would be much better served by a system based on free markets and free trade between nations.
For critics like Smith, mercantilism represented everything that was wrong with economic policy when amateurs get involved with running the economy.
At the time when Smith wrote The Wealth of Nations, British economic policy was predominantly in the hands of aristocrats who tended to have little or no experience of how a modern economy actually worked. And so they fell back on the tried and trusted policy of mercantilism as a way of maintaining economic prosperity.
But Smith argued strongly that, though there was undoubtedly a role for government to play in regulating the economy, the key decisions about the production and allocation of goods should be made according to the operation of the free market. The market, not well-meaning amateurs in government departments, would determine what, where, and at what price goods would be produced.
Smith was sure that without the constraints imposed by the mercantilist system, the economy would be able to generate considerably more wealth and prosperity. In putting forward his economic philosophy in The Wealth of Nations, he was challenging the prevailing orthodoxy and trying to convince his readers that there was a much better, more efficient way of doing things.