I'm going to apologize in advance because I don't watch the show, but I have a friend that was obsessed with it, so I'm interested to see how it all "came together" at the end now that it is over.
Regarding the 2 1/2 hour show: they know coming up to the end what has or hasn't been said and how they want to end it. They could have just explained more of it BEFORE the last second so that you can have an ending AND all the answers. But I don't think they want to answer everything somewhat to just leave it out there and let people talk about it for years, and also somewhat because they wrote themselves in a hole and needed to just let some of that stuff go.
I've many times read that the creators had an idea for the beginning and for the ending, and then didn't know what would come between. Since the network seemed to have lengthened the show quite a bit past where the writers originally intended on having it, then they probably had to write a lot of filler stuff in the middle to keep it going. But is that really a reason to just say "annnnnnd, all that stuff was not real and you were all dead"? That just makes me wonder over and over if the writers original outline said:
I. Cast of characters come to island (unsure why)
II. Characters mingle
III. The island is ... (protected? saved? I'm still not exactly sure what happened because no one in this thread or the others that I have read through today really lay it down .. probably so they don't give away spoilers)
IV: Everything else that wasn't tied up this way didn't happen.
I know I'm oversimplifying it here, but there's a difference between a TV show and a movie: I expect sometimes that a writer of a screenplay gets a great idea, and they get it made into a movie, and it makes a great point, and they leave it open ended so that you think about it for a while, and tell your friends "hey, watch this movie, it will make you think afterwards." They only have 2-3 hours to get you to this point, so it makes sense.
A TV SHOW however (this one as an example) had what ... 80-100 hours to tell its story? So at the end of that, when they are tying up loose ends and coming to a close, I really don't want stuff to be open to interpretation, because you already spent 100 hours of my life explaining it to me little by little. You had all the time in the world to get me all the answers that you needed to. And unless you're planning on doing "Lost 2", then its never getting answered, and people spent a lot of time not getting answers that they waited every week to get.
Yes, I'm hating on Lost with little or no right to, but just place any TV show in here (Sopranos?) that leaves the end open after taking your time and feeding you advertisement for 6-7 years.