Dear Peter,
Certainly, you are more than correct.
The Petrine Primacy is different today, for starters. But no Orthodox theologian, no mainstream Protestant theologian either has ever denied that there was an accepted Petrine Primacy centred on Rome in the first millennium.
That didn't prevent a pope from being condemned (Honorius) and others from being reprimanded and even refused sainthood for their lapses (Liberius - although he is a full saint in the East).
But when Honorius was condemned, the Byzantine East only sung the praises of the successors of Peter at Rome all the more loudly.
The estrangement process between East and West was just that - a process. The date of the "final break" set 1054 AD is a superficial one since other Churches in the East (such as Kiev) had very good relations with Rome after this date.
The daughters of St Yaroslav the Wise married RC princes and kings in the West - there is no record of them ever having to have joined the Catholic Church in order to so do. The granddaughter of St Volodymyr the Great married a German prince who soon died and she became an anchorite/hermitess living in a hollow oak tree and is today a Catholic saint.
When Ukrainian Orthodox found out about St Edigna, they began making pilgrimages to her shrine . . .
Although the Orthodox Metroplia of Kiev was under the EP, that influence did not steer that Church away from Rome - the EP's influence was neutered by Turkish domination. To ensure that the Church of Kiev "behaved" loyally towards the EP, Stauropeghial Brotherhoods were empowered by the EP to act as overseers over the Kievan Orthodox bishops (which included both Belarusyan and Ukrainian bishops at that time). The Church of Moscow was considered by the Western-educated and intellectually sophisticated Kievan bishops to be a backwater at that time ("barbaric Muscovy" as St Peter Mohyla and other bishops of the Kievan Baroque habitually referred to it).
This tended to reinforce the Orthodox bishops' resolve to "change patriarchates" and move to Rome. There is copious historical evidence at the time of the Union of Brest (which has been much maligned, unjustly, by Orthodox historians) to suggest those bishops really didn't see much difference, other than of a local Latin one, in a Faith held in common. In any event, they saw the Council of Florence as a normative standard confession of a united statement of faith and praxis - reflected in the articles of the Union of Brest.
And Roman Catholic commentators in contemporary times have read the works of the Kievan Orthodox bishops and teachers of the Baroque era - Sts. John and Paul of Tobolsk, St Joasaph of Bilhorod, St Dmitri of Rostov, St Theodosius of Chernihiv, Bl. Lazar of Chernihiv, St Peter Mohyla, St Innocent of Irkutsk and others - and have commended them as great luminaries of the entire Church etc.
As you know my inclination to go off on tangents (but interesting ones, no?
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), I will stop here.
Alex