IMHO The show was suffering from GRR Martin’s writing style in the books. Which I think is also the reason why he still hasn’t finished the series.

To write a novel, you basically need two styles. One is to follow the flow of the story and let it unfold, let it take you with you wherever it wants to go. He’s great with that. But you also regularly need to switch to a more focused approach that captures this meandering and “railroads” it in the direction of your planned ending/finale. Which he just cannot seem to get to. The last season(s) had the dilemma, that there were so many loose ends and character arcs to combine and “railroad” to the end, that the writing and story just had to suffer.

There was either the need for way more seasons, or to capture the story earlier.