Humanity, or at least the Westerosi, will most likely come to the understanding (after a horrific amount of violence) that the Others are not people but persons, and will most likely intermarry etc etc.
Nah. There is literally nothing in his book to suggest that he's setting up "the Other are just misunderstood, we need to build bridges" hippy dippy bullshit. If anything, the Other are a personification of hatred, war or even a force of nature - I could make a far more convincing argument that they embody climate change (as foundationless and nonsensical as that is) than what you suggest here.
The way the story is set up, the big idea is that there is a large threat to all of humanity and humanity is too fucking dumb to pull their shit together, get over their ignorrant and petty little squabbles to unite against that existential threat. Which is kind of the main failure of GoT S8, when it makes Cersei the final boss. It's literally the antithesis to what the book is going for.
George RR Martin's pretty naive to a lot of aspects of combat, the heavy prevalence of warrior women is cringe inducing and out of touch with how pre-industrial societies operated.
Brienne of Tarth and Asha Greyjoy are like the only female fighters worth a damn in the entire book series and Brienne is mocked or pitied by literally everyone she's ever met for being a female warrior - including Catelyn Stark who takes her into her service. The Sand Snake sisters amount to neither jack nor shit in the books iirc. I wouldn't call 2 characters, one of which is treated like a joke by everyone, a heavy prevalence.
Also, female warriors (both historical and as literary figures) have been around for thousands of years. Atalanta, Boudica, Joan of Arc and Tomoe Gozen, just to name a few.
I don't think it's a matter of scope but rather a matter of the plot being very much obvious at this point. Everything is way too telegraphed so the SUVERTING MAH EXPECTATION the series is known for will not work without risking massive changes. Which is a fitting fate for this kind of post modern type of writing.
The thing with Martin's writing in ASOIAF isn't so much that it subverts expectations, it takes an axe to certain established tropes and replaces them with a strong internal logic.
In a regular fantasy story, a noble deed by a main character would be either successul or at least have a positive outcome/payoff later on for him, in ASOIAF, it can get that character killed.
Ed Stark, for instance, spared Cersei, tried to do the right thing about her bastards and he got incarcerated for it. He believed the promises of being send to the Wall if he pleads guilty to protect his family and he gets his head chopped off. Why? Cause he sucked at court intrigue and expected people like Littlefinger to be honorable.
The Red Wedding was another culmination of a character paying for an earlier mistake. In this case, someone broke his marriage vow and thus insulted a really,
really vindictive motherfucker. His attempt to mend the situation didn't pan out, cause said motherfucker shopped around for better alternatives and sold him out to the Lannisters.
Point being, in the books, actions have logical and consistent consequences based on character goals, their emotions, experiences and so on. People make mistakes and this drives the plot, but it happens in a believable manner. Characters have goals and work towards meeting those goals and their actions realistically reflect that, based on the characters personality, limitations and conflicts with other characters.
Dumb and Dumber, however, thought that the story and its popularity relied on Shyamalan-tier "WHAT A TWEEEEST"-crap, so they procedurally employed more and more tropes that the books originally tried to avoid, in order to set up shit. Suddenly, you have plot armor, deus ex machinas and utterly illogical shit popping up left and right.
Their goal was no longer to make a story that progresses in a believable and logical manner, their goal became coming up with twists as outrageous and unexpected as possible, cause in their eyes, that's good storytelling. S8 is a giant failure extravaganza without even a single plot-twist that isn't utter garbage, chosen only to go "LOL DIDN'T EXPECT THAT, DID YA?!".