It's really amazing that GoT didn't go from "okay" to "terrible", or from "outstanding" to "meh", which is the most common thing. No, it really went from "outstanding" to "terrible".
In the first seasons, working off of GRRM's writing, the seasons literally subverted expectations, just as the books. Then Hollywood had to get involved, because source material didn't exist, yet. At that point, 'subverting expectations' became the meme it is today.
(Nearly) Every action movie seems just so formulaic. Action movie - hero doesn't want to be the hero for (insert dark/dramatic reason 1). Hero soon finds that being the hero is better for the world than not, regardless of personal consequence. World warps around hero to make sure s/he doesn't die. Bonus points for cool car chase, gun fight, or explosion. Nudity that doesn't move the story forward except to show that Hero likes to have sex isn't required, but will add to the box office, because people like boobies and butts.
Hero stories have been following the same template since the dawn of mankind.
For an example, try to fit the Epic of Gilgamesh (as an extremely old conserved folklore tale) or Don Quixote (as one of the oldest and most famous literary works) to this framework - you will either fail or need to contort them quite a bit, or ignore large chunks.
A friend of mine, when he heard about this in the class, argued "but I want to create something unique that doesn't fit to this or anything else, like... the Matrix!". The professor was speechless for a moment but could keep his calm :)
The two most recent off the top of my head:
* Don’t look up
* James Bond No Time to Die
Of course the books still aren’t done so if they waited we’d still not have anything to watch. IMO from what I’ve read about the books it sounds like they could have cut out less and made the early seasons last longer without it dragging too much.
Seemed to me they ran out of characters to kill, made some filler to get to the last season and then rushed a bunch of stuff badly.