I have to respectfully disagree with you. As you say you missed all of season 5, the season that answers most of you questions. If you did not watch it you did not see who the smoke monster really was, how he was made and what he was trying to do. If you had watched you would have found out that everything Jacob said about the island was the truth, it was the cork in the bottle.
Yes like any good book, questions were left unanswered. The show, from the start, was a thinking man's who. The writers choose names very carefully and wrote little hints as to what is happening. There are reasons that John Locke was named after the philosopher. Before I can tell you what I think about the Walt and Faraday I have to clear some other things up.
I have to say I do not think the show was ever not wrapped in symbolism. But what is really important is that you said “lead writer had refuted the theory that everyone was dead, in purgatory, in heaven or in hell. Yet, at the end they're clearly in some sort of afterlife.” No they said the Island was not purgatory and it was not. The island was real. I would try to explain more to you about the island but since you did not watch the last season that it would really just be a waste of time. I do not mean to flippant about that but what the island is was explained and you chose not to watch it. In the flash sideways time is not a constant, that is the point. They all lived their lives and then came together at the end once all of them were dead, it can be confusing if you keep trying to apply time to the flash side ways. You cannot do that, time is not what you think it was as they were waiting. That is why Ben was not in the church, he was waiting for whom he leaned to love, his child and her mother. Again you missed all that since you did not watch the last season.
In the end you were really supposed to decide what that show meant for you. I think the real issue with people that did not like the ending was that they want to be told everything. They want everything to be explained to them, that is how T.V. works now. I go back to my original point that it was a thinking mans show. The more you have read, especially philosophy the more there was to get out of the show.
No you do not know when people died. Not all of them. They died at different times as they lived their life. They all met up before going to heaven. In the end they were all part of a great battle that could have been the end of the world. They were changed for the better and they wanted to met before moving on together. That was the flash sides ways in the end that was the fake world, it was only built by them, so they could all be together. It may seem like that was a type or purgatory I think of it as more of a waiting room. I would not say there were suffering, so it would be a stretch to say it is purgatory.
I guess what really bothers me is that this post is rated insightful and it was written by a person that did not even watch the whole series, and the most important season was missed all together. Would we think so much of a book review if the writer had picked random pages to read, and then complained when they said it seems like the books jumps around a lot.
Again I have say it was a thinking mans show. As all mysteries are, if you wanted to just watch a show that has everything explained to you then yes, you were watching the wrong show. If you wanted a show that was more like a well written book and you had to think about it to see how it changed and moved you then this show was for you. I have to say there are not may question that I feel were unanswered. I am sure there will be a number of post that put it all out there for the ones that choose to be told what happened then to work it out themselves. But that is like playing a video game by following the walk-through what is the point? You might as well wait for the movie.
// That is what I think anyway.