Game of Thrones was the TV show of the 2010s. Everyone and their cousin watched it. There were plenty of reasons for this, from the rich writing to the nuanced characters to the nice blend of back-stabbing intrigue with fire-breathing dragons. All of this built toward the promise of an epic climax where all the audience's questions would be answered and long-standing plot arcs would finally be resolved.
Instead, the final season started trashy, only to immediately go all "Dracarys" and ignite every plot point into a miserable heap of hot flaming garbage. Story structure and basic reason went up in smoke. Frankly, the show did not so much end as just in die in a confusing tragedy that still makes no sense.
Dothraki Tactics
The Siege of Winterfell opens with the Dothraki sitting on their horses outside the walls of Winterfell, preparing to charge the armies of the dead. They are armed with their traditional curved swords, arakhs.
The problem is that everyone knows that the only things which can hurt the dead are fire, Valyrian steel, and obsidian. So in effect, Daenerys threw an entire heavy cavalry unit at the dead with no functional weapons. Thankfully, Melisandre shows up and conjures a flaming enchantment on their weapons. And even then they all die. There is literally no scenario where the Dothraki are tactically better off charging the dead.
Melisandre's Return
Melisandre returns just before the battle, appearing out of the night. And interestingly, she comes from the same direction as the White Walkers.
Assuming she somehow managed to cross the North without starving, being slain by the Others, or succumbing to the elements, she still has no reason to know when the battle is about to start. It seems the night is long and full of plot holes.
Dothraki's Return
All of the Dothraki are killed during the Siege of Winterfell. All of them. This is a major plot point that is explicitly acknowledged in dialogue.
However, the Dothraki magically just get better and reappear in time for the Siege of King's Landing. Did some arrive in on boats across the Narrow Sea, ignoring their fear of water? Did a few have scrolls of resurrection given to them by Melisandre as secret followers of her fiery cultish religion? This lack of forethought can only be compared to what comes out the backside of a Dothraki horse.
Zombie Dragon's Icy Fire Breath
Is there a better summary of fantasy stories as a whole than the fact that "zombie dragon's icy fire breath" is its own category? Too bad it was handled so poorly.
Magic systems need to work with their own internal logic in a story. When the White Walkers turned Dany's dragon Viserion into a wight, the dragon's breath was powerful enough to bring down the Wall--the same Wall that stood for millennia and kept the White Walkers out since the Long Night. But during the Siege of Winterfell, Jon crouches behind some rubble to hide from Viserion's breath attack. How are some chunks of rock able to repel Wall-destroying dragon breath? Perhaps they should have just built the Wall out of that debris.
Varys's Betrayal
Varys is a big supporter of Daenerys. He spies for her, but he also works to help her from a continent away.
In his life, he has seen both good and bad Targaryens rise to power. And Varys is also the smartest political manipulator alive at this point in the series, having decades of experience operating in secret. So in contradiction of everything established about his character over seven previous seasons, he rashly blabs about his treasonous thoughts on multiple occasions and gets himself killed. Neither his betrayal nor his clumsy handling of events make any sense.
Sansa Snubbing Daenerys
Sansa and Daenerys have beef with one another throughout the final season. Sansa led the North to secede from the Seven Kingdoms, a gambit that was quashed by Daenerys. But really, the bigger issue here is that Sansa resents Dany sleeping with her brother Jon.
Sansa is too smart of a political operative by this point in the series to think that being catty toward the Mother of Dragons is a good idea. There is no good reason to be this passive aggressive high school drama, especially when there are far greater concerns.
Daenerys's Madness
As the granddaughter of the Mad King, Daenerys was closely watched from childhood to see if she too would go mad. But she never did. She fought through multiple wars in Slaver's Bay, two conflicts to unify the Dothraki, went up against the Warlocks of Qarth, lost her husband Drogo, and gained her crown multiple times over, all while staying sane.
Then in Season 8, she spirals into insanity, remorselessly slaughtering innocents as she fashions herself into a Mad Queen. She even dresses like a bad guy in a scene where she confronts her troops while garbed in black, the entire sequence invoking the imagery of 1940s fascist movements. There is no reason for any of this. It is not the conclusion of her character arc. It is just acting out of character.
Sam's Survival
There is so much wrong with the Battle of Winterfell that it seems irresponsible not to pay more attention to it (something the show's creators should have done). One example is that Sam somehow lives.
Sam is Jon's best friend. Over the series, he rises to become both smart and capable despite starting out the series as an incompetent coward. But when Jon runs through the zombie-filled carnage in the battle's climax, he passes his friend, pinned to the ground, about to be killed by a wight. Jon leaves his friend to die so that the battle can be won. Thankfully, Sam apparently remembered to put on his plot armor that morning, which is the only explanation for his survival.
Exploding Army
When Arya kills the Night King with her Valyrian steel blade, it is a nice surprising twist. No one saw it coming. Sure, Arya never had a history with the Night King to make this personal for her the way it would have been for other characters, but this just adds to the unexpected quality of the kill.
But for some reason, when he dies, everyone in his army dies. Not just the undead either. All of the White Walkers explode in icy bursts of CGI carnage, the entire army going down with a single dagger thrust. This is, needless to say, incredibly stupid. None of the established magic makes this seem likely. At the very least, the other White Walkers should survived.
Bran's Relevance To The Show
The entire Battle of Winterfell revolves around Bran. He is the apparent savior of the world and of the troops, but he literally does nothing the entire battle except temporarily greensee through a flock of birds.
Then, in the series finale, Bran is crowned king. Because apparently the most important qualifier for a good king is that they have a good story. Except by the logic, Tyrion, Jon, Daenerys, Arya, and even friggin' Reek are better-suited to sit the throne. It is just a good thing that the show's creative team does not get to impact government in real life.