The Dany storyline didn’t need anymore fleshing out. It was all there.
Bran’s stuff is what needed more time. One, maybe two more episodes could have helped.
Full seasons plus two more would have been ridiculously slow moving with way too much filler.
Ridiculously slow moving?
There was an established pace to this show from season 1-6. Every season 10 episodes of approximately 1 hour in length. I don't know how much more they would have needed to flesh it out properly, but my biggest problem with seasons 7 and 8 was pacing, which was directly related to length of seasons. I don't care one bit that some episodes were longer. It felt all wrong.
They could have used some of that time to prepare us for Bran being named King at the end of it all. He felt like an "important" character in quotes. He never once felt like he was destined to reign over kingdoms of humans. And then at the end of it all, the most wise person (was he a person still?) in the land allowed a sell-sword with no experience to be made Master of Coin before skipping out on a Privy Council meeting to warg into a seagull to go find a pissed off dragon.
Again, there are lots of things to nitpick, but the biggest shame of it all is how rushed the final seasons felt. They don't fit with the rest of the series and in ten years when people go back and re-watch or get into this series for the first time they will come to the same conclusion and scour the internet wondering what happened and why it is so different.