So what's the problem? Few things, but big ones. Two things particularly, which line up with the odd conclusion in a particularly gruesome way. They both have to do with imagination, unfettered imagination, creation. The things you've created, and your responsibility toward them.
The show has been sketched out a year at a time, brilliantly; it is a living breathing thing, which lends it all the power it has. The problem, for me, is when that stops being true. When the plot isn't left alone to figure itself out, because an endpoint has been decided, and nobody feels like doing the work at the end of the season to tie all the threads together.
Fanboys, sometimes they hate the fact that stories work this way. They want it all stitched up ahead of time, with a plan on the books. I don't really understand why, but I know that there's not a show on television, or a novel ever written, that works that way. Things change, stories evolve and grow up, or the people creating them change, or lose interest. But fanboys, sometimes they are loud. So the showrunner has to say, "I know what the last thing is." The last image, or the last word of dialogue, or who's left standing. Maybe it's true, maybe it's a bluff.
It would be better if it were a bluff. Because you can't have it both ways. You can't say that the story tells itself, pat your back egregiously for the "artistic" details you've chucked in for no clear artistic reason, while also reassuring the fans -- whose opinions don't really matter anyway, because all you owe them is a story, including me, which is why I feel comfortable writing about this -- that there's an endpoint, a reason for it all, a final mystery. That all will be revealed.
Trust the story, and it will be. I think what I reacted so violently to, this finale and the last one, was the exceedingly inorganic, forced nature of the revelations, at the last second. Not organically developing out of the story told over the preceding nineteen episodes, and the threads of deeper meaning and juxtaposition that they afford, but a determined weeding out of tools and images that didn't fit the finale, when it was time to write the finale. That's distinctly irreverent, toward the material, toward the story itself, and to your writers. I think what happened here was less a issue of forethought and planning, and more a loss of nutsack at a crucial moment. A dedication to reaching ideas long plotted out, working against the grain of the story itself, to arrive at treasured endpoints that no longer signify.