Series Finale

I was intrigued and happy with where they were going with this for 2 hours and 20 minutes - and then the last 10 minutes killed it!

The alternate universe is some kind of purgatory???
Desmond was the key to nothing???
What is the island??? Why can it time travel (by turning a magic wheel?)?
So many key questions unanswered - i'd like to list more, but my baby is crying.