The Fathers did not include the Filioque because it was not an issue for which the Council was called. That does not mean that one can just add it.
Speculations as to the nature of Divinity have always been part of the Church, but it is one thing to speculate and another to claim that it is what the Church officially holds to be dogma.
The problem with the Filioque did not usrface until it became the dogma of the Franks, who wanted to impose it on everyone, and even called the Greeks heretics for having "omitted" Filioque from the Creed.
The Filioque was treated more-or-less the way one treats Limbo or the way the RCC treated the Immaculate Conception until the 19th century -- some believed it and some didn't, and no one was penalized for not believing it until it became dogma. Last time I checked, Chalcedonian Creed is dogma. Just as you can't add something to the dogmas of Immaculate Conception, by the same token you can't add Filioque to the Creed simply because you believe it.
The Popes up to the 11th century understood that and, even if they personally agreed with the theology of Filioque, refused to add it to the Creed for the same very reason.
The fact is that the West does not need the approval of an Ecumenical Council to compose prayers for its liturgy.
The Fathers did not include the Filioque because it was not an issue for which the Council was called.
Exactly! Thus it is imposible to say that it is contrary to the faith of Nicea or ever condemned by any Church council.
The Filioque was treated more-or-less the way one treats Limbo or the way the RCC treated the Immaculate Conception until the 19th century -- some believed it and some didn't, and no one was penalized for not believing it until it became dogma.
Thus to profess it (as did St. John Chrysostom who presided over Ephesus) cannot be heresy!
Last time I checked, Chalcedonian Creed is dogma.
The last time I checked the Catholic Church has never denied the teaching of Chalcedon.