With the story line they had the only ways it could have improved are as follows to tie of plot points from earlier series.
1. Jon fights the Night king but the Night King withdraws, raising the dead to keep Jon away from him.
2. The undead raised in the crypts, Starks, turn out to be not under the control of the Night King and defend the people in the crypts against the Night Kings armies who break in. (There must be a reason for "There must always be a Stark in Winterfell").
3. The hot springs in winterfell could actually have been maintained by a sleeping dragon who rises to help defend the Starks. (It goes back into the catacombs beyond the crypts after the battle).
4. In this episode, Drogon should have first torched Jon Snow after he had killed Daenerys but it had no effect on him except singeing his outfit. So Drogon then torched the Iron throne and then bowed to Jon's will. This plot device could then have been used for Jon to gain control of the Unsulid and Dothraki to send them on their way to end slavery. Grey worm just doing nothing was just crazy. He'd have tried to kill Jon instantly.
I watched a video by a professional screenwriter on how he would have done the WInterfell episode and thought it was much better. In his version, Jorah dies in the first wave of assault on the white walkers, some of the dragon fighting scenes would have been changed but the best bit was where he had Bran going back into memories:
-first memory he goes back to before the mad king was mad, tells him he needs to stock wildfire as the dead will come. This causes him to go mad and he starts shouting burn them all and kills everyone (this is a call back obviously to Hodor so works well). He leaves, realising it was all his fault.
-he then decides to go even further back and stop the night king from being made by warging into him, it flashes back to the bit where the 3 eyed raven told him he should never stay in memories too long or he will be lost forever, he tries to stop the children of the forest buy fails and then realises he cant comeback out and becomes the night king.
- this answers why the night king wants to kill him so much as it will stop any chance of him being wiped out.
-jon gets past vicerion and attacks the night king who catches him mid-flight like he did with Arya. Earlier on in his version he has shown that Beric dies and Arya takes his face. In the background you see Beric as a white walker, he jumps in and slays the night king, then removes the face to reveal Arya.
There were some extra bits he added in and he changed some of the sequence of events in the episode, but it just shows how subtle changes could improve this season so much IMO.