Really? That's not what the Second Council of Lyons said:
"We profess faithfully and devotedly that the holy Spirit proceeds eternally
from the Father and the Son, not as from two principles, but as from one principle; not by two spirations, but by one single spiration. This the holy Roman church, mother and mistress of all the faithful, has till now professed, preached and taught; this she firmly holds, preaches, professes and teaches; this is the unchangeable and true belief of the orthodox fathers and doctors, Latin and Greek alike. But because some, on account of ignorance of the said indisputable truth, have fallen into various errors, we, wishing to close the way to such errors, with the approval of the sacred council, condemn and reprove all who presume to deny that the holy Spirit proceeds eternally from the Father and the Son, or rashly to assert that the holy Spirit proceeds from the Father and the Son as from two principles and not as from one."
And Florence made it even clearer:
"In the name of the holy Trinity, Father, Son and holy Spirit, we define, with the approval of this holy universal council of Florence, that the following truth of faith shall be believed and accepted by all Christians and thus shall all profess it: that the holy Spirit is eternally from the Father and the Son, and has his essence and his subsistent being from the Father together with the Son
, and proceeds from both eternally as from one principle and a single spiration. We declare that when holy doctors and fathers say that the holy Spirit proceeds from the Father through the Son, this bears the sense that thereby also the Son should be signified, according to the Greeks indeed as cause, and according to the Latins as principle of the subsistence of the holy Spirit, just like the Father."
This is what was taught up until these days. I don't see the wiggle room to say it's only an economic sending in time without denying that the Councils say what they say. I wonder what RCs you might mean?
If it's a heresy, it's a heresy, and I should be Orthodox instead. If it's not a heresy (and I'm not convinced it is), then it still didn't need to be added to the Creed.
Filioque is theologically solved in my opinion. RCatholics are very clear in explaining that what they want to say with it is not causationg in the Son, but the economic sending of the Holy Spirit to the World by the Son.
What remains is related precisely with the governance of the Church. The Roman Church is not fixing the Creed because they do believe they have the prerrogative of changing it unilaterily if the Pope so wishes, despite the fact that this approach goes against the very concept of Catholic authority.
Once the governance issue is theologically and formally solved, it will be just a matter of deciding if the filioque is altogether dropped - for, despite the intended meaning, in that particular context it cannot mean anything but causation - or if something equivalent to "and to the world through the Son" to better clarify what is meant.
There are others, but I believe it is these two that are the real blockers for union.Filioque doesn't count as a blocker? Basically, we'd somehow have to cancel Lyons and Florence as well as Vatican I, or you accept "the Father and Son together are the one principle of the Spirit". Given the current situation, the former is just slightly less impossible than the latter.