Playing devil's advocate a bit here...
By the Orthodox Church's self-understanding of the meaning of "Catholic", 19th century Rome is no more Catholic than 16th century Boston or 21st century Los Angeles. They are all separated from the full grace of the Church.
I agree that the (somewhat) recent
self-understanding of some
Orthodox understand Western catholics in this way, but I must disagree that this is how things actually are
, or that it is how the Orthodox communion at large has understood things over the centuries. A "catholic" is a baptized Christian joined to the mystical body of Christ in the sacraments, under a bishop with Apostolic succession. More shades of nuance could be used of course, but in simplistic terms, that's what it means. The "Catholic" Church is the local Church; the pre-eternal Church made manifest in space and time as baptized Christians gather under their bishop to celebrate the Eucharist. This is the Church confessed in the creed, this is the full, complete, whole Church which has the fullness of grace and the means of salvation. And this is the truth of the matter whether or not each local catholic church is united to a particular geopolitical superstructure.
This way of looking at the Church was gradually de-emphasized in favor of speaking of the Church in terms of the oikomene
; or "all believers everywhere," catholic as "universal" rather than "whole." But "church" in that sense is not the same as the ontological Church; the mystical Body of Christ.
The situation we find ourselves in now is that there are Catholics who are in communion with each other, and Catholics who aren't. But, as Fr. Laurent Cleenewerck says, "'the Catholic Church' contains in itself the fullness of means of grace, sanctification and salvation, whether or not 'united' into a particular geopolitical superstructure. In other words, Cyprian of Carthage, Stephen of Rome and Firmilian of Caesarea can still be bishops of the catholic Church and saints in spite of their ruptures of communion. The Churches of St. Thomas in India, or those of Ethiopia were always one, holy, catholic and apostolic even when disconnected from Rome or Constantinople. It also means that the saints (of East and West, for instance St. Francis of Assisi and St. Sergius) do not drop in and out of the catholic Church because their patriarchs are quarreling over who knows what. Likewise, the idea that salvation is tied to a particular worldwide organism becomes obsolete" (His Broken Body, p. 345, Kindle edition)
Why then is there validity to Roman patrimony but not Protestant? It all developed in separation from us.
Well, Protestantism isn't a monolithic reality. Which Protestant patrimony would we be talking about? Lutheran? Presbyterian?
The guideline set forth in Antioch was: Parishes and larger units received into the Archdiocese retain the use of all Western rites, devotions, and customs which “are not contrary to the Orthodox Faith and are logically derived from a Western usage” antedating the Schism of 1054.
The important point in this, for this conversation anyway, is that it be "logically derived" from the tradition of the first millennium. It implies that there is a stream of tradition that has existed from this time to our own, and that anything within that stream that is not contrary to the faith of the Fathers is acceptable. What in Protestant tradition could really fit into that category?