You need to go reread the Naturalization act of 1790. It most certainly does say that. I'll excerpt the salient portion for you.
And the children of citizens of the United States that may be born beyond Sea, or out of the limits of the United States, shall be considered as natural born Citizens: Provided, that the right of citizenship shall not descend to persons whose fathers have never been resident in the United States:
The part you cite has to be taken into the context of the fact that a person born anywhere outside of the United States of citizens of the United States will also be a citizen, and also a natural born citizen, BY RIGHT OF BIRTH. The portion you cite means that the person born of a non-citizen father has no right-of-birth status and has to go through the legalization process, not that they can never become a citizen.
As I said, the Act has been replaced, but its value now lies in the fact that it defines what the founders meant by “natural born citizen”.