For some reason this got removed from r/asoiaf, but luckily it's been mirrored at r/unpopularopinion:
Game of Thrones is rapidly declining in quality
David Benioff and D.B. Weiss were hired to adapt a book, not to write its conclusion - They are skilled at adapting book content for television, as is clearly evident from seasons 1-4, but once they ran out of content, they had no choice but to write their own with only breadcrumbs left by GRRM. We can see that their writing is below average to say the least.
The show was greenlit with the expectation that it will not surpass the books - When the show started filming in 2009, we were just two years away from ADWD, and the first season aired in the same year. No one in their right mind would have guessed that the book writing progress would slow down considerably. The show was supposed to slowly sail through books (which it had done). TWOW and ADOS would be obviously released before the show ran out of content.
HBO management had a say in the show's production - Some characters, namely Bronn, were included more in the show because HBO saw Q ratings for the character and forced the production to include the character more. I think it wouldn't be far-fetched to assume that HBO marketing had their hand in many more writing decisions. Maybe most of them were minor, but who knows at this point.
GRRM wrote himself into a corner - with a story this expansive and large, it's no surprise he is having trouble bringing all these characters and their standalone story arcs to a satisfying conclusion. What could be considered the hardest part of any story, the ending was left to DnD, who, as we can see, aren't great at writing stories, let alone write the conclusion to A Song of Ice and Fire.
The show's target audience changed and influenced the direction of the show - This show is arguably one of the most popular shows of all time and the most trending thing on TV right now. Back in Season 1, a majority of the audience were people who were either: a) ASOIAF fans or b) fans of fantasy. Since then, the epic battle scenes, subverted expectations and tits on TV brought in a large audience that didn't care much for worldbuilding, lore or the name of the Lord of Storm's End. They cared about TITS, chopping off heads, dragons breathing fire and suspense. What has once been just one element of the story became its sole component - most of S7 and S8 is insane CGI scenes, explosions, battle sequences and edge-of-the-seat action. Slower episodes like 1 and 2 have garnered a mixed response from the more casual side of the fanbase. This can be most clearly seen when comparing IMDB episode ratings, newspaper critic reviews, as well as from the general fan response on social media.
D&D shot themselves in the foot when they decided to end with Season 8 - HBO themselves offered D&D funding for more standard-length seasons, but D&D declined because they cannot conjure meaningful storytelling for 10-20 more episodes. What we can see now is a concoction of GRRM's breadcrumbs and piss-poor D&D storytelling adhesive that tries to hold those crumbs together. Not a very good duo.
The original version, IIRC, was longer and included points on how D&D were good at writing small scenes within the context of the existing material (e.g. Arya and Tywin).
Related:
Game of Thrones is all payoffs now, with little storytelling - "As the storytelling speeds toward the show’s conclusion, it increasingly doesn’t tell stories. It sets stories up and pays them off, and hopes that you don’t notice it didn’t do anything in between. In the summer of 2016, I lamented something I noticed taking over blockbuster filmmaking: the loss of the second act. The second act is, broadly speaking, the middle of the story, and in classical Hollywood screenwriting, it was usually most of the story. After a setup of 15-30 minutes, it would encompass the next hour or so, before the story would wrap up over the final 15-30 minutes. The second act is important because it features the character and plot development that got the story from point A to point B. It is about the journey, in other words."