Been a fan of GoT for years, I watched the series a few times.
The beginning of the show that included book material made the most impact, it kept the characters stories interesting, however once the book material had run out i.e after season 5, things kind of went a bit bad...not terrible but seasons 6-8 could've been better.
Although, season 6 did have a great storyline and of course included Battle for Winterfell (known as another name but can't type it), then Daenerys finally setting sail for Westeros which was a long time coming that season wrapped up nicely.
However, it seems that the writers then forgot the potential of the characters, season 7 starts off with Jon meeting Daenerys then it seems in a blink of an eye the show takes a steep fall.
The writers truly rushed seasons 7 and 8 and it no longer feels like you're watching a show with great lore, you're just watching the downfall of Daenerys happening so quickly. She loses everything the moment she gets to Westeros, 6 seasons preparing her to be there and within 13 episodes it's all gone...I'm not a fan of Daenerys but I'm pretty sure that's just poor writing choices.