There probably wasn't much wrong with Season 8 on paper. It just needed 3 seasons to do it.
Season 8 - The Night King and his armies invade and destroy half of the 7 kingdoms. There needs to be at least 3 big battle here, including the destruction of Winterfell. He is finally stopped by the united armies of all Westeros including Lanisters, Starks, Grey Joys, Rohirrim, Star Fleet, etc, rally together to stop him. Bran accidentally becomes the night king as he wargs back in time to stop the night king in the past and has to be killed by John Snow (That theory is just better)
Season 9 - Immediately at the end of the war with the night king, Cersei betrays Danny and butchers a large part of her army. Danny loses some battles to Cersei (her Dragons can't be everywhere, and Tyrion has held back her dragons power to save civilian lives). A long war of attrition ensues, and Danny slowly pushes Cersei back to Kings Landing. The North - tiring of fighting another's war (and wanting to return home to rebuild following the Night Kings wrath), sends a delegation into Kings Landing to negotiate a power-sharing/surrender deal. (The idea being that Cersei can live her life out, holding power in Casterly Rock). Danny launches a surprise attack and destroys Kings Landing in an attempt to end the war and to finally rid the world of Cersei. [This needs to be much more marginal than in the show, whether it was right or night, and should have brought up parallels to Hiroshima/Nagasaki etc.] The North and some of the other regions declare independence after their Nobels and men are killed in the destruction.
Season 10 - Danny realises that the advice of Tyrion had led her to lose battles again and again because he's weak-hearted. Finding out he tried to save his brother in Kings Landing, she locks him away. John Snow initially argues that Danny had to do what she did, but wrestles with his consciousness. He goes to the North to ask them again to bend the knee to Danny. They reject his offer, and he returns to Danny empty-handed. Unknown to him, she launches a surprise attack on several castles held by the North and their allies. The Castles are destroyed either by armies or dragon fire but some Nobels survive as they prepared for such eventualities with deep underground tunnels. John and Danny prepare for their wedding. Sansa and Arya create a plan to use her many face abilities to kill Danny. But to do that they will have to kill their brother first. The Starks meet John in secret and beg him for his help. He says they shouldn't have betrayed their Queen, and if they bend the knee once more he will beg her to forgive them. They beg him to reconsider but he refuses. Arya can't bring herself to kill John. Tyrion is executed in his cell along with thousands of others. John and Danny arrive for their wedding. John goes to kiss Danny and plunges a dagger into her heart.
A few changes there - but mostly sticking to the same script - but I think with much deeper emotional consequences. The whole thing was rushed
Urgh, this shit is currently sitting on 50k upvotes on Reddit. I get that alot of people are pissed off with the last couple seasons, I certainly am, but dumb lazy posts like this getting so many supporters are a big problem.
I didn't think it was possible think less of a story than D&D have done, and then I saw this. Naturally the echo chamber are downvoting anyone that says this is a bad idea and two whole seasons of just The Night King and a whole season dedicated to the war with Cersei would need endless filler.