Everyone dies (eventually). We never find out what the island really is. The sideways universe didn't (really) matter. Simple questions like what happened to Walt and why he was special will NEVER get answered.
But none of that matters. The finale was still spectacular, because what Lost delivered last night wasn't the logical conclusion many hoped for, or even the "character drama" the writers promised. It was an emotional conclusion, a literal and figurative goodbye funeral for your favorite show, a finale that eased you into the passing of a dear friend. And better still, it left you with the promise that everything and everyone you loved on the show would be okay.
The show cunningly delivered everything your heart wanted while patently ignoring everything your brain wanted.
Two and a half hours was just long enough to feel almost but not quite too long. By the time it ended, you were worn down emotionally and needed a break, and you were READY for it to end. And ready in a good way. Any shorter would have been unsatisfying. Any longer would have been too long. And by putting the two-hour special on ahead of time, ABC made sure that the hardest of the hardcore fans who might have wanted a five-hour finale got one, too. Insidious, really.
The most blatant, illogical way Lost helped to ease your suffering was by letting you see all your old friends again, living and dead (or at least most of them). Even the ones who died in the early seasons and weren't really relevant anymore! Everyone likes to see an old friend, at least for a few moments, as long as you don't have to get into any awkward conversations with them. Just enough to remind you of the pleasant memories you once had, not long enough to remember that you might not have really liked them. And better yet, you were told they're all going to be okay!
We were all spoiling for some sort of fight, so Lost delivered one. And not only delivered it, but delivered it in a way that we had our cake but got to eat it, too. Jack dies, but he's okay. Locke dies (again-ish), but he's really okay, too. It doesn't matter that if you look deeply at the conflict it doesn't quite makes sense; the point is we HAD conflict. And more importantly, that the conflict was resolved. ...
This was a particularly tricky one because not only did characters forgive—and, just as importantly, accept forgiveness from—one another, by emotional connection the show's creators asked us for forgiveness for all the show's flaws. Because what was happening on screen mimicked what was happening to us in front of the screen, it was a neat little bit of transference. We're all flawed, but in the end none of it matters as long as we love each other. So, really, you don't ever need to know what the island is ...
A Passing Nod to Logic
It's long been known in TV and movie land that as long as you have some sort of passing nod to logic, and enough things happen that no one wants to look too closely at, you can get by with it. Lost again gave us just enough logic to get through the finale. Uncorked island = bad. Corked island = good. Smokey must uncork island. Jack must cork it. That's all you need to know, and that's all you GOT to know. It worked in the moment, which is all that mattered in this case.
You PERSONALLY Got to Say Goodbye
All those moments between the commercials that were love letters to fans? Those were also YOUR GOODBYE NOTES to the show. You got to express your grief and sorrow, and experience those emotions with millions of others. That's powerful, cathartic stuff. And it was unrelenting (again, in a good way). You knew that EVERY break you'd get another note of loss and farewell. Absolute genius.
Notice how so many people were SMILING all the time? And not only that, but they were huge, benevolent, warming smiles (Locke and Kate are particularly deadly at this skill). Smiles in this context are a universal human signal of pleasure and happiness. Did you wonder why everyone smiled so damn much during that last 15 minutes? That was why. Sure, we're at a funeral, but everyone is constantly smiling and laughing, so it's all okay (and the dead guy isn't really dead).
We Were Told to Move On
When you go through the grief/loss cycle for anything, the last step in the cycle is always acceptance. In this case, we were all explicitly told many times by the show's characters and even the show's creators (if you watched the special) that everything is okay, everyone will be fine, and most importantly it's okay to move on. It's not just time to move on, it's the right time. ABC also handled this masterfully, signaling us so far in advance that this was happening, and then the Lost creators spend 2.5 hours holding our hands and easing us through to the end. Double genius!
So in the end, what matters is not that there was an end, but that it FELT like an end. And in that, Lost was brilliant. As the old saying goes, "The heart is forever making the head its fool." And fooling us into a great Lost ending was much better than any logical ending ever could have been.