Hello Hobie,
You quote Cardinal Newman, but miss the point entirely. The point that goes hand in hand with the scripture I quoted 'capture every thought for Christ'.
It is not the act of worship or celebration or festival that makes it pagan but the object of that worship and the intention of the heart.
A simple demonstration..
2 neighbors get up every morning, face the rising sun, prostrate themselves and offer praise and thanksgiving. One is a pagan and one is a Christian..
you can't tell which is which unless maybe you overhear their prayers or know their hearts..
For one is worshiping the creation (the sun) while the other is worshiping the creator of the sun, the True God, Father, Son, and Holy Spirit..
Everywhere the Gospel has come, local customs, culture, celebrations etc... have been reordered to the proper object of worship and thus are no longer pagan!
Pax et Bonum