
Amy K. answered 05/05/19
B.A. in Piano Performance with 10+ Years of teaching experience
Excellent question, and you are absolutely correct to be a little puzzled about where this work falls in history!
Fux deliberately looked to the past with his analysis/teaching of counterpoint. He's one of the first in music history to write about past techniques rather than the techniques of his contemporaries. Fux believed that the music of the 16th century, Palestrina's in particular, had the firmest foundations, especially as a way to break into the theory of his contemporaries. J.S. Bach also used Palestrina's work to inform his own rules of counterpoint.
As a consequence of looking to the 16th century, however, Fux abandoned tonality, which can be argued is an easier approach to teaching counterpoint. That way, you don't have to worry about making sure you're writing "correct chords" on top of just learning the voice-leading parts!
There's a neat introduction to the history of "counterpoint" in the 1971 edition of Gradus ad parnassum translated and edited by Alfred Mann (with collaboration of John Edmunds) if you want to check that out; I think there may be a few ebooks floating around the internet via libraries and such. Hope that answers your question! Not sure if there's a way to follow up on here, but best of luck in your music studies!