Yeah, I’m pretty sure it was mentioned that they built the wall to keep bad people/zombies/undead in the north from coming south.
Jon Snow was always an imbecile, and as he became the central figure the problems with the character manifested themselves in the narrative arc. But at least Kit Harrington is a decent actor even if he was directed to act like a mopey goth teen all of the time. On of the biggest problems was the casting of Danerys; Emilia Clarke seems like a nice person and she’s attractive, but she’s about as credible at portraying a strong ruler and “Mother of Dragons” as Elijah Wood would be in the role of a Harlem Globetrotter, and when she was on screen with other main characters it was just painful to watch how better actors like Iain Glen and Peter Dinklage had to carry her. Sophie Turner was another one and was not helped by the Littlefinger marriage plot, or how she almost spontaneously went from “Little Sparrow” to “Badass Warrior Queen”. There were other poor casting decisions but none which impacted the show quite as badly, and much of the criticism of Brann had more to do with the fact that he just didn’t have anything useful to do, irrespective of the actor’s thespian talent or lack thereof.
Except nobody believes in the whitewalkers and their army of wights. The wall is clearly an attempt to be a (much exaggerated) version of Hadrian’s Wall, and the wildlings are the Picts, and other analogues to Roman Britain. I was never so enthralled with the show (or the novels) that I overlooked this lack of originality; George R R Martin clearly read The History of the Decline and Fall of the Roman Empire, mashed it up with a bit of Celtic and Norse lore; threw in some Mediterranean Sea Peoples and North African coastal cultures, added a bit of post-Late Bronze Age collapse, and then threw in some magic and dragons. What made the show interesting were the characters and how richly they (some of them) were developed. But in the last few series, and particularly amplified in Series 7/8, the characters just started doing stupid things for no reason other than to feed the plot, and once you start feeding your children to the Plot Monster, it just gets more ravenous. This resulted in deeply developed storylines being dropped in toto while new motivations and characters pop up without really adding anything novel.
Drawing everything to a conclusion is a problem with any sprawling epic (and why Justified spent so much of its fifth series killing off characters) but with a show like this that is driving to a specific conclusion it is crucial that at least the key plotlines come together in a plausible fashion, and that didn’t happen. Jamie sleeping with Brianne and then rushing back to be with Cersei is pretty much a nutshell explanation for everything that was wrong with how Benioff and Weiss ended the show; it undoes all of the character development of every character involved for a completely nonsensical resolution that doesn’t feel remotely satisfying. And the stupid thing is, with just a few tweaks it could have been fine. Jamie could realize that Cersei is going to destroy everyone and caught in a tragic trap, has to sacrifice both of them. Instead…a ceiling falls on them. Like they’re in a Monty Python skit. I could choke past the incredibly bad tactics and stupidity of military leadership if there were at least a dramatically satisfying conclusion, but they way this ended played out as a comedy of errors. I’m just glad Diana Rigg got out early in the sevent series before things got really ridiculous and they lost any ability to write witty dialogue for any character. (I’m half of the opinion that Rigg just walked on set, sneered at the dialogue written for her character, and essentially played herself in the role.)
Oh well…at least we got to see The Mountain and The Hound face off in a mostly-satisfying conclusion. Everything else about how the show ended was pure shite, including the sitting around in a counsel voting on who should be king, because the way momentous way to end an epic saga with with a little casual bureaucracy and petty bickering. Tyrion didn’t even drag a chair across the dias to signal his disgust with the petty stupidness of the proceedings.
Stranger
I’m pretty sure the people who originally built the wall believed in them. Also, if a huge backstory about the builders of the wall is in the books, don’t bother to post it, I only watched the TV show.
Nobody believes in them NOW, but they believed in them back when the wall was built.
An appropriate end would have been to have everybody at the council drink a toast with Bran from a couple of bottles of wine pillaged from Lady Olenna’s cellar. The vintage Joffery got. (Fade to black.) 
I didn’t find that satisfying at all. Some stumbling around in a quake, stereotypical reversals of fortune, and then they both fall to their deaths. There was no character resolution at all.
Sure, but why continue to maintain the wall? The Night’s Watch is clearly a place to cast off unwanted or bastard sons, so that at least makes sense, but maintaining this enormous fortification would take a massive amount of effort as the wall would be subject to erosion, and we see none of that.
The Hound flings both of them to their death after Zombie Mountain does his signature “gouge their eyes out” maneuver. It isn’t really the ending I wanted to see, but at least they didn’t have the Mountain falling into a pit of sewage and drowning or something. I’m a little pissed because their timing was off and a lost a bet on which episode it would occur in so as to not distract from the main plot, but then, we got no resolution to any main plot element as far as I can tell, and now their is an untamed, uncontrolled dragon flying around Westeros probably eating whatever random serfs that are still left in this post-apocalyptic shithole ruled by a sullen teen in a wheelbarrow. Deal with that, Bran!
Stranger
Easy to explain. It is not subject to erosion. It’s a TV show. Plus, they’ve been doing it for 1000 years, who are YOU to decide not to keep doing it? (what they ask people who ask the same questions you are)
The Nights Watch does some maintenance, but the Wall is largely held together by magic, at least that’s how I recall it. That’s why Wildlings can occasionally go over or around, but the Others can’t cross until the dragon wight takes it down.
Most of the forts along the wall are abandoned, so it’s not like the Nights Watch is actively maintaining more than a tiny portion of it.
One thing that seemed like plot armor at first blush but upon thinking about it seems like a subversion of expectations is the final dragon’s not attacking Jon. If you were someone’s friend and you saw them over the dead body of your mom you wouldn’t always assume that they were the attacker.
I liked how they played up the idea that dragons are as smart as or smarter than men, but even they have to make hard judgement calls sometimes, rather than have a supernatural sense of who did what that fantasy sometimes brings to both humans and non-humans.
What exactly, are Bran’s powers as the new Three-Eyed Raven? Is he just an omniscient being for everything that has happened in Westeros? Do his powers extend to seeing everything that will happen in Westeros?
Further, we know he can warg into different animals. Do those animals potentially include people? If so, can his warging be subtle enough to merely cloud perception, cause people to forget things?
What I’m stumbling towards is, what if all of the stupidity was to leave the GoT universe with one dragon, who is basically omnipotent if he stays away from ballistas, and have Bran permanently warg into Drogon? Stash Bran’s body in the roots of some heartwood tree, and let an eternally living, omnipotent dragon, with all of Bran’s Three-Eyed Raven knowledge, be the ‘King’? Akin to the situation in Frank Herbert’s fourth Dune novel, only it’s a dragon that’s the Tyrant, not a sentient sandworm.
Oh, and as a bonus, Drogon can just throw Blondie off his back when she goes nuts.
He already warged into a person. Remember Hodor?
True, but then he also needed him to do one specific thing decades later. It wasn’t made clear what would happen if he warged into a person just for a moment and kept his intended effect limited to a more proximate period of time.
I’ve heard some (novel-based) speculation that the “Mad King” may have been driven mad after an attempted warging by Bran’s predecessor as three-eyed raven.
It’s more than seeing. His “memory” power appears to be a kind of time travel. He was almost able to talk to Ned Stark in one of his memories, and the Night King found him and marked him in the past. Most tellingly, Hodor’s stroke and subsequent speech aphasia happened when he was a child but was caused by his death many decades later. If Bran hadn’t been bridging the past and present at that moment, would Hodor have had the stroke?
And of course, every other line out of his mouth in season 8 is something like “you became what you were meant to be” or similar, implying that he can also see the future. And also implying that the outcome to the conflict was preordained, so probably best not to think too hard about it.
Realizing, or more likely, guessing through wisdom, that everything was meant to be retroactively isn’t impossible, but the only way that time travel could have worked is if everything was preordained. Time travel is usually a deal breaker for me and that was the worst part of the series for me, but I got over it because it happened so late I was invested in the series and plot-wise it was only a mechanism to explain how Brann was able to escape.
What will be funny to see heads explode if the books end the same way. But he’s not finishing the books. Why would he? Other than just a cash grab.
I assume that the HBO money was enough that book royalties are not enough of an incentive to finish the series.
Couple this with the weak ass scene with him telling Arya to go home and forget about her kill list (and her thanking him <insert angry face here>) just before the Clegane Bowl kicked off and it rendered 2 interesting and long running story lines to a shitty and very unsatisfying end.
The books are already different enough that they can’t end the same way.
Colon and Nobby would be trying a million-to-one every other day if that happened. Only with a ballista. 
The books are never going to end, so the abortion we got from the morons is going to be it, I’m afraid. Martin has written himself into so many corners that he can never make it all work. Not in three lifetimes.