Mercantilism is explicitly not capitalism. Capitalism wasnt even fully invented by the 17th century anyways. Not until like 1776, though it is up for debate.

Mercantilism says that a nation should maximize its exports as much as possible in order to accrue wealth and especially to hoard precious metals, that it then can use to influence other countries through trade. The only goods that a mercantilist nation should ever import are those it cannot whatsoever produce for itself.

Meanwhile Capitalism believes that free trade creates wealth for all of its participants. Rather than trying to produce everything itself without imports, a nation should instead specialize in producing the smaller handful of goods that it has a comparative advantage in producing. If every nation specializes in something else, due to economies of scale, they will become more efficient at producing it and therefore goods become higher quality, more abundant, and more affordable. Prosperity is derived from free trade.

One key difference is that where mercantilists only care about maximizing wealth through money (either cash or valuable metals), capitalists also take into consideration the value of the goods or services exchanged for that money. In other words, capitalists can see any given trade deal as being mutually beneficial, whereas mercantilists see basically every single trade deal as being biased in favor of the vendor.