The attention to detail has probably suffered due to the size and scope of the show growing. It's easier for show runners to be able to manage smaller plot details when it was in the early seasons. It's a lot harder when they're choreographing major battle scenes every other episodes.
Even under better oversight, the reality is the show has transitioned from its early seasons, partly due to popularity, but partly due to the story. Even GRRM eventually has to stop killing off the main characters and build a traditional narrative.
I don't think D&D have managed that transition great, but, it's adequate, and then reality is, there isn't much to compare this to. The closest comparison in pop culture is Peter Jackson's Lord of the Rings, and a single season of Game of Thrones is roughly the same amount of screen time as the trilogy, but has a lot less time in production to bring it to screen.
There show has flaws, but there's still a lots of good stuff there, IMO. The acting is still pretty solid out of most of the players (dialogue scenes like Jaime/Tyrion or Hound/Beric are treats to watch), production values are pretty incredible for a weekly show (visually, it's hard to argue they haven't done the world GRRM created justice) and the current and recent seasons, despite the writing shortcomings, benefits from the great world building of GRRM and early seasons that it makes it easier to forgive some of the sins.
It's not perfect by any means, but it's the best in genre. There's room for improvement, and, if someone else can bring this type of ambitious story to life, they'll have Game of Thrones to thank for getting the chance to do so.