1. The Orthodox Church isn’t ONE.
Christ declared definitely that His Church would be one fold under one shepherd, but there is no agreed authority among the Orthodox Churches.
There are at least 16 different Orthodox Churches existing independently of one another.
Like all schismatical Churches, it has ended by splitting up into further divisions. Just as there is no united form of Protestantism, there is no one united Orthodox Church.
2. The Orthodox Church doesn’t claim infallibility.
It has no way of deciding matters of faith or morals infallibly. What is its teaching on birth control, divorce, IVF, medical and health ethics?
On all these vital matters it has no authoritative or binding statement.
Indeed, when asked about the Orthodox position on birth control, Patriarch Bartholomew, the Greek Orthodox archbishop of Constantinople, replied that ‘according to a long-held tradition, the Greek Orthodox Church avoids dictating or making categorical decisions of a social or ethical nature.’ (Time Magazine, 5 May 1997)
3. The Orthodox Church isn’t catholic, i.e., universal.
It is mostly confined to the Greeks and Slavs and their descendants wherever they have migrated.
Its total following is only around 220 million, and it doesn’t make much missionary effort.
4. The Orthodox Church is not apostolic.
It lacks the continued juridical succession of apostolic authority.
The Orthodox Church acknowledges a bond with definitely heretical Churches, but they acknowledge no real bond with the Catholic Church.
They reject the unity that only the Church of Christ can give and therefore lack the supreme spiritual authority of the Papacy. They tried uniting around the Patriarchate of Constantinople, but that wasn’t sufficient to prevent secular princes demanding a separate church for each kingdom.
A unity of reverence isn’t enough. Only a unity of obedience suffices:
“If a man will not hear the Church, let him be as the heathen." (Matthew 18:17)
5. The Patriarchs of Constantinople were all subject to the Pope at first.
Before the Great Schism commenced by Photius in 867 A.D., the Patriarchs of Constantinople were all subject to the Pope. There were no Patriarchs of the Greek Orthodox Church.
The First Council of Constantinople in 381, for example, demanded that the Bishop of Constantinople should rank next after the Bishop of Rome, and before the Bishops of Alexandria and Antioch. The Eastern Bishops affirmed at the end of The Council of Chalcedon in 451, “Peter has spoken by Leo.” A century and a half later, Pope Gregory I wrote, "Who doubts that the Church of Constantinople is subject to the Apostolic See?" The Patriarch of Constantinople, and all the Eastern Bishops signed the formula of Hormisdas, who was Pope from 514 to 523. That formula contained these words,
“We follow the Apostolic See in everything and teach all its laws. I hope to be in that one Communion taught by the Apostolic See in which is the whole, real, and perfect solidity of the Christian religion.”
6. Politics, not doctrine, started the Greek Schism.
In 861, missionaries from Constantinople converted the Bulgarians. To bring them under the jurisdiction of the Latin Patriarchate of the West rather than have them under the Patriarchate of Constantinople, Pope Nicholas I appointed Bishops for the Bulgarians in 866.
But partly this was also to maintain Rome’s political authority over Constantinople, and the Greeks resented it. Photius, Patriarch of Constantinople, wrote to the Pope in 867 condemning the Catholic Church. Although provoked politically, he also made various doctrinal charges. The schism started when the Pope excommunicated Photius, who retaliated by excommunicating the Pope.
After Photius made peace with Pope John VIII, he was duly recognized as Patriarch of Constantinople. This reconciliation lasted until Photius died, but then trouble started again.
After various difficulties, Michael Cerularius, the then Patriarch of Constantinople, renewed the break with Rome in 1054. He wanted to be universal Patriarch over the whole Church. Appealing to the political importance of Constantinople, he won over the Emperor. And since then, the Patriarchs of Constantinople haven’t submitted to the jurisdiction of the Pope or sought his confirmation for their appointments.
But Greek Delegates to the Second Council of Lyons in 1274 (and at the Council of Florence in 1439) admitted that they should. They sought a return to unity with Rome. On each occasion, however, on their return to the East, national interest repudiated their admissions.
7. Opposition to the Papacy defines Orthodoxy.
The Orthodox Churches are in agreement with Catholics on most things: the main difference is the Primacy and Infallibility of the Pope.
For example, the Greek Churches believed in the Immaculate Conception until the advent of Protestantism. They had nothing against the doctrine in itself. Even under pressure of Protestant opinion, although they wavered, they never denied it.
The denial only came when the Pope defined the doctrine in 1854. Merely because they were opposed to the Pope, they wished to manifest their opposition.
8. What starts in schism ends in heresy
Heresies start by either denying the teachings of the Catholic Church or by rebelling against her authority.
The Gnostics, Manichaeans, Arians, Nestorians and Eutychians started with doctrinal error and ended by defying the authority of Rome. Similarly, Protestantism started with a denial of teaching and ended by a denial of authority.
But the Greek Church started by defying the authority of Rome and has ended by denying some points of Catholic teaching, including:
that the Holy Ghost proceeds from both Father and Son.
the supremacy and infallibility of the Pope
the right to give Communion under one kind only
the Catholic doctrine of the particular and general judgments
the Catholic doctrine on the nature of purgatory
the Immaculate Conception.
The Rev. C. J. MacGillivray, in his book, Through the East to Rome (1931), says that after spending time in the East as an Anglican working for the reunion of Greeks and Anglicans, he realised it was impossible:
“Compared to the Roman Catholic Church the so-called Orthodox Church is just a collection of fossilized and moribund fragments of what was once a great and living Church. Indeed it seems to me to be a great object lesson in the disastrous consequences of abandoning the rock on which the Church of Christ was built.”
He converted from Anglicanism to Catholicism.
If there's nothing even in principle that could make you abandon Orthodoxy for Catholicism, I'm not sure what the point of an argument would be. Your mind is made up. And while I appreciate that you think you've shown all the 8 reasons are somehow wrong, so far you haven't got past number 1. But as I've said: you've plainly shown that hostility to the Papacy is the essence of Orthodoxy. Although Orthodox and Catholics agree on most things, that is the root error leading to all the others.
Infallibility isn't what most people imagine: it's limited to very specific pronouncements and doesn't work like that at all. In principle, no pope could contradict the Church's teaching on homosexuality.