First and foremost, people need to take a step back and probably rewatch the entire show all the way through before hating the writers because of their ending.
From the beginning of the series I knew this as a Suspenseful, Scifi-ish, Drama that would weave and swerve and take us all for a fun ride. At the end they took us to the height of the ride and dropped us from the cliff, as if the world was ending...and then dropped us on a nice landing pad as if we had just come down....a little bumpy, but good.
1) The Writing was PERFECT, They wrapped up all their loose ends that they needed to, left enough for people to think about and ask questions if they want(and create fanfiction out the yin-yang), and stayed true to their main themes throughout the entire production run.
2) The Acting was good...in fact most of these actors were never big names, but I will forever remember them for the work they put out...they were all given very difficult roles to portray and they did them beautifully, I was amazed.
3) If you were watching for all the small issues...every little plot point and how it tied into the big picture, and looking at it all as a story with a message at the end, then you were watching what I was watching. If you watched a show with awesome action and good plot but that "shortchanged" you with the ending, then you weren't watching it as it was intended...remember the messages throughout the show, this was all very much set up to tell a moral or an ending at the end.
This show was very much written with the Well-Made Play Formula and the Spirit of the Greek Tragedies in mind. The Theatre and Literature Scholars of the group can agree with me...it was written with the Overarchign story the entire time...very much a Greek Tragedy that happens to twist the ending...but leaving a lot of loose ends...Euripides is a good starting point. This show was never meant to be something that was 'just a scifi show', it was always meant as a work of art and a complete story, and this ended exactly how every story should.
"All of this has happened before, and all of it will happen again."
So Say We All!