Yes, to the explanation above. The island was not purgatory - it was 100% real. They survived the plane crash and lived out everything we saw on-screen.
My issue with Lost (and I really did love it) was that the introduced the "flash-sideways" in the final season which was really too late, and they presented it as a consequence of the bomb going off at the send of season 5. By that point, we were looking for things to be tied up, not a new mystery, so the actual tie-ups seemed rushed and lost (no pun intended) amongst the confusion of the flash-sideways. This meant that the final episode was essentialy a reveal/explanation of the flash-sideways rather than a proper ending to the whole show. IMO the church scenes would have still worked, and been even more powerful, if season 6 had been written differently throughout. Also, the fact that the flash-sideways ended up being purgatory, basically allowed the casual fans to take one message only from the finale - the answer was purgatory, and therefore think that they were right all along. The decision to show the plane flying overhead as Jack died (the rest leaving the island but this wasn't clear enough) and then the wreckage over the end credits, just added to the confusion.
Then Alan Dale did a load of TV interviews in which he said he didn't really understand any of the show but thinks that they were dead all along so more people jumped on that (we'll always believe good, dependable Jim Robinson) despite more regular actors saying the opposite.
I truly do beleive that Lost was tightly plotted for the majority of time and not just made up along the way. I think they were damaged badly by the writers strike which meant changing the ways in which the stories were presented and having various seasons on inequal length and of course there was additional padding in early seasons which came back to haunt them as this situation unfolded.
Many of the mysteries were explained - the polar bears were brought to the island for experimentation by the Dharma Initiative. They were given intelligance tests (fish biscuits) and trained to turn the wheel so that the DI could understand how the island worked. They broke out and roamed the jungle after Ben wiped out the DI.
A lot was left unexplained though and that is still frustrating. The fact that the numbers were just coincidence all along and many other things which were not definitely presented as mysteries on screen but had a lot of fans theorising - I, for example, was a huge believer in the theory that Charles Widmore was his own grandfather think they missed a trick in not addressing it.
Overall, I think Lost suffered from being the first tv show of its kind. The gradual introdiction of supernatural elements didn't sit well with audiences who thought they were watching a pshycological thiller about survival and the links between the survivors, but many popular shows now are supernaturally themed - Lost paved the way for that. I also don;t think a lot of folk had the patience to wait between episodes, especially when so much happened - it was hard to remember and keep up, week by week, and even worse in the longer breaks between series due to strikes. Introduced now, and available to binging, I think it would have a very different audience and reception.
I remain confident though that there will be a reboot/sequel with the children of the original group going to the island to learn about their parents' fate - Aaron, Charlie, Ji-Yeon, Clementine etc. Walt as leader, maybe.