So having been an Orthodox Reader, you are now agnostic? - if I have the wrong person, forgive me. I do not judge you, but wonder why you lost your faith - not expecting an answer on a forum.
I wasn't a reader, so perhaps you are thinking of someone else on that point. Regarding why I am no longer a Christian, I'll try to give an answer as best I can, though it is really a matter of more factors than I could include here.
About a year and a half ago I started struggling with some issues. One set of issues was, 1) whether Genesis should be taken literally, 2) what it would mean for Christian beliefs and practices if Genesis was not take literally, and 3) the anthropological consequences of a literal and nonliteral interpretation of Genesis. Another set of issues was much more fundamental, and was basically the standard philosophical question asked by many people: how can I be sure that what I believe is true? At that point I realised that I had never really examined why I should be a Christian to begin with. I just sort of dove into Christianity nine years ago without really thinking about whether I should instead be a Buddhist, or Muslim, or Atheist.
I had read books on Christian apologetics before. I knew quite a few evidences for Christianity from my Protestant days, and some from my Orthodox ones. But I had never attempted to examine Christianity from outside of a Christian mindset. When I had considered arguments for and against Christianity before, I had always interpreted the info through a Christian lense. Unfortunately, when I took the lense away, I was not able to find something solid in Christianity to grab on to.
The obvious response is, "that's what faith is for!" Only, it's not. At least it shouldn't be. You can't have faith in something that you don't believe to be true. I mean, if I said "Sure you don't believe that George Bush is an alien, but you just have to have faith!" would that mean anything to you? You can't (and shouldn't) have faith in something that you don't accept to be true. Using the faith argument (or Pascal's wager), I might as well be a Muslim or Buddhist. "I can't find anything solid in Islam to make me think that it's the truth... but I'll have faith in it anyway". This wouldn't be acceptable, would it? The concept of "just having faith" is only a justification for maintaining already-present beliefs when you are having doubts; as odd enough as it might sound for me to say, I respect that. However, it is irrational to ask someone who rejects Christianity outright to apply that idea of faith in his life. What would that be asking, except that someone have faith in what they believe is wrong?
I don't want to get into all of the issues I have with Christianity that prevents me from being a believer in it, though I'll give a few. First, I don't think that Orthodox epistemology solves what it purports to solve. It does not clear up which aruthorities should be consulted when, it does not clear up how we can know that Orthodoxy is correct, and it does not clear up who it is that we are to go to for a final answer on the questions that matter the most. Various attempts at an answer are given for all these things of course, and I am not trying to denigrate these answers; I just do not find them peruasive myself. Second, I think that some of the Christian ideas are bunk, and these I am not so respectful about. For example, I think the idea of an eternal hell is complete B.S., and it has caused a great deal of psychological problems (generating fear, anxiety, etc.) throughout the last two thousand years of human history.
Third, I don't trust the Christian Church to decide what morality is, and trust the Bible even less. I'm not going to get into particulars here (I will elsewhere in the future), but I'll just say that I've read far too much that makes me doubt Christianity's ability to give the absolutely correct moral code that it claims it can. Each generation has dealt with problems, and things change over time; there is no indication of a universally accepted moral code, except that code which apparently almost all people (even those who have never heard of Christianity) acknowledge. The Judeo-Christian tradition of course has some brilliant moral ideas, such as the Golden Rule given by Jewish teachers and repeated by Jesus. There are also, unfortunately, a lot of bad ideas, some of them supposedly from the mouth of God Himself.
Another issue involves science, of which the creation/evolution debate is a part, but a very small part. As time has gone on, God has been more and more a God of gaps. Whenever there is something mysterious or unexplained, God is the answer; whenever an answer is found, God is removed from the equation, or leastwise relegated to merely "sustaining" things. As time has gone on, God has had less and less gaps to fill. I do not know that all of these gaps will some day be closed. Probably not. But enough gaps have been closed that atheism no longer seems so crazy. The Greeks and many others have had nontheistic ideas about how we got here, but it is only recently that people in the Western world could really accept atheism. By coincidence, it's only recently that atheists wouldn't get imprisoned or executed for their atheism
A lot of the thoughts I had about Christianity, a lot of the arguments in favor of it, I also found alternative answers to (or I just found out that I was plain wrong). A few of these arguments that I was mistaken on (IMO) were: 1) there is no morality if there is no God; 2) the lives/miracles of saints prove Christianity is correct; 3) every society has believed in a god or been religious, therefore religion must be necessary; 4) studies have shown that intercessory prayer works; and so forth. Once I looked outside of Christianity for a bit, I was suprised how quickly answers to these types of arguments came in. And more suprising for me was the fact that many times the answers came not in some diatribe against Christianity, but in some news report or scientific study.
And, to wrap up, I'm not a Christian because I think it can be demonstrated that the prophecy made by Jesus that "the gates of hades shall not prevail against [the Church]" has not come to pass. The early Church saw in this term a number of different promises: that heresy would not prevail, that division would not prevail, that worldly powers would not prevail, that church-wide sins would not prevail, and that personal sins would not prevail against individual Christians. I think there is historial evidence that the prophecy has failed to protect the Church in all of these ways.
Anyway, hopefully I have not offended anyone. I don't claim that the above is irrefutable. Indeed, I might change my opinion on something next week, for all I know. There are some thoughts though, for what they're worth.