Well, my understanding is that the Orthodox Church has the teachings of the early church, like baptism, divine presence in the Eucharist, apostolic succession.
If I wasn't Orthodox, that would mean for me that I very likely gave up Christianity. I admit the possibility I could have a mind-blowing revelation that the kosher Judaizer tendences of some in the early Jerusalem church were right, or that Jesus was only a human Messiah, but still was a Messiah, and in that case I would join some very small group. But I think that kind of revelation would be very unlikely, absent a time machine, plus I doubt those things would be right.
Judaism is the base of Christianity, but I would not go to Judaism, not because I am not an ethnic Jew, but because I love the image of God in the New Testament. Alot of the image of God in the Old Testament makes me recoil, when it takes about such strict laws of executing heretics, flogging people, not to mention all the kosher rules and customs. I think and want God to be a God of love and mercy, so it is not a model I would join. Judaism's main idea is monotheism, and that IS something I could go to.
So I would become a theist. I think Thomas Jefferson and the founding fathers were Deists- they did not believe in Jesus' miracles, but believed in God in the classic nonChristian monotheist sense. I read that some Bolsheviks, like Maxim Gorky and perhaps Lunacharsky, did believe in the Lord God despite being nonChristians, and they called this understanding "Bogostroitelstvo." They saw God as being a collective, sharing commune of humanity combined with God. They had different ideas about what this meant. I think the movement might be associated with Transhumanism in English.
So I accept the Orthodox faith as the faith handed down by the apostles. If it turned out to be false, it wouldn't be on something like the Pope being an overarching infallible replacement for Christ on earth over all the church. That sounds so ridiculous and almost blasphemous to say that one person who is not God can be unable to make a mistake, especially when we see cases of Popes torturing people to death. if he thinks that is a good church decision, I don't trust him to be unmistakable when making up theories either. Sorry.
To reject Orthodoxy would have to mean that Christianity itself was deeply flawed, that the wonderful things I want to be true are not. I would still love God and go with the faith of the American and [some] Russian revolutionaries. But for that if a big IF again. I would again probably need a time machine to prove one way or the other. I am still on a spiritual journey spending time learning about Jesus and Christianity. And even if it is wrong, it is still a wonderful journey because it is very inspiring to see how a person can teach so much love, mercy, and understanding about God, be executed for it as a bad criminal, and have this faith spread around the world. I want Jesus to be resurrected like all the other good criminals. There are many many criminals, and many of them are good.