Not true; St. Athanasius and the Cappadocians, and indeed Tertullian who coined the word "Trinity," followed the tradition of the Apostles and defended their doctrines with Biblical quotes. You should try reading their works some time; if you did, you would find them equally awash with Scriptural references and denigrations of Hellenic philosophy.
This is a completely false statement on your part, as this link to the BibleHub concordance shows:
http://biblehub.com/concordance/s/substance.htm
A word that appears 99 times in Scripture I think we can all agree is not foreign to it. But you just basically accrued ninety nine counts of (I believe accidentally) disseminating a false statement
Here is where you are getting confused: the specific phrase used in the Nicene Creed, "of one substance," homoousios, is not used explicitly in the New Testament. But one can regard it, by the standards of dynamic equivalence translation as used by the NIV and other modern Bibles, as a valid thought-for-thought dynamic equivalent of "I and the father are one."
On the other hand, since Jesus never says "I am like the father," which the Semi-Arians argued for (homoiousios) or "I am unlike the Father," (heterousios, the preferred Arian term), we can reject these alternatives as un-Biblical.
Arius was specifically the Classical Theist you ought to be taking issue with; he was the one who latched onto the Pagan philosophical concept of the Logos as defined by Philo and the neo-Platonists and tried to apply that concept to our Lord, even to the extent of contradicting the very passage that identifies our Lord as Logos, because that passage also calls Him God. Arius tried to weasel his way around this with the "God according to honor" argument, but that failed, because again, homoousios is a valid expression of "I and the father are one."
No, its puzzling to many because they were poorly catechized or not catechized by their respective churches at all on what the Trinity is, and what it means for us in terms of Salvation. Its tragic how many Lutheran, Episcopalian and Methodist churches bear the name "Trinity Lutheran" or "Trinity Episcopal Church" or "Trinity Methodist Church," but almost never preach about the Trinity and why the Trinity and a belief in it, indeed, an emulation of it, coming from us, is imperative for our salvation.