The show got 'worse' because many of the more experienced actors have had their characters die on the show. I don't think the writing has changed all that much, except that there's more focus on action than narrative.
Actors like Aidan Gillen and Charles Dance could carry scenes all by themselves.
Rose Leslie and Kit Harrington had chemistry on screen (and off screen
). Clarke and Harrington simply don't.
Carice van Houten by herself is a good actress but without Stephen Dillane as her counterpart to manipulate she has no role to play.
A few stars have really improved their acting during the course of the show. Especially Sophie Turner.
Take this scene for example, which is supposed to be 'tense'
Lady Sansa is defiant, steadfast and compassionate all at the same time. Turner plays Sansa really well.
Clarke has about two different emotions and her voice rarely changes as she reads her lines.
Note how scenes like these are also recorded very slow for no particular reason.
Now compare it to this 'tense' and slow scene. Just a random roundtable discussion with high stakes:
And this runs in the entire show. Cersei talking with Qyburn and Euron just doesn't have the same weight as a conversation between Tywin, Jaime, Cersei and Tyrion.
You won't get a lengthy monologue because there's no one left to give them. The writers have to work with the characters that are left.
Who are either young and inexperienced, side characters with elevated roles (such as the Unsullied Commander) or characters without the acting skills of the heavyweights.
So when you look at who's left alive and grade them on acting skills:
spoiler (click to show/hide)
S-tier A-tierCersei Lannister
Tyrion Lannister
B-tierSansa Stark (getting up to A in some scenes)
Samwell Tarly (in some scenes Sam is A-tier)
The Hound
Bronn
Tormund Giantsbane
Jon Snow (but it depends on who is counterpart is)
C-tierArya Stark (Maisei Williams is hit and miss)
Jaime Lannister
Brienne of Tarth
Qyburn
Davos Seaworth
Varys
D-tierBran Stark
Daenerys Targaryen (Clarke is just all over the place, sometimes she gets up to B but it is mostly shit especially her scenes with Harrington)
The Mountain
Euron Greyjoy
Gendry
Yara Greyjoy
Grey Worm
Missandei
Podrick
You can easily spot the problem that the later seasons of the show had. Because more and more 'good actors' die and more and more mediocre actors take center stage.
Last week another character died which kept Clarke's scenes together. So as writers you do the only thing that you can, you have them fight and you make it look flashy.
And even that went wrong with the D-tier sand snake sisters in an earlier season. And honestly we can't blame the writers.
They couldn't predict that Clarke wouldn't develop better acting skills over the course of 8 seasons or that the kid that they cast to play Bran Stark would continue to look bored.
Because the show is structured in a way that most of their top talent would die during the course of 8 seasons it was inevitable that in some areas the overall quality would take a hit.