The story-writing is so illogical and betrays so many of the characters' arcs. Let's start with the character assassination of Dany. Now let me acknowledge that she is probably going to go Mad Queen in the book as well and there are hints from the very first book that this may happen, including bursts of anger and paranoia (to be fair, it's justified). However, since the books are POV, I am expecting for Martin to clearly show her descent into madness.
However, in the show, they have not gone nearly done enough to imply she would murder innocents just because. Sure she has burned enemies before, but it was always a military opponent or other sort of threat. It was always based on principle. She has specifically gone out of her way over and over again to protect the innocent, including just three episodes ago when she put her army and two remaining dragons on the front line against the army of the undead. Her decision to murder the civilians AFTER winning the war is completely irrational and out of place with the character as developed on the show, and the fact that Rhaegal, Jorah, and Missandei died and Jon is a Targeryan is not enough to justify this shift. If they are trying to say she went crazy, they needed to more to establish that. If they are trying to say she just gave into evil impulses, then we needed that to be better established by her doing more morally questionable acts (the sorry attempt with the Tarlys fell flat because her actions were in line with the actions of other Westerosi leaders in the show).
Next we have Tyrion. Why in the fuck is he suddenly such an idiot? He honestly deserves to be executed for his lack of good council. Based on how easy Dany took Kings Landing in 8.5, she should have gone straight there when she landed in Westeros and taken it right away when she still had three dragons and the Lanisters hadn't developed the big crossbows. Since she hadn't "lost it" yet, she presumably wouldn't have killed innocents. Tyrion already has massive strikes against him for stupidly having faith in Cersei in 7.5 (hey let's risk the life of our biggest ally to try and catch a member of the army of the dead to try and convince Cersei to help us, even though that notion is OBVIOUSLY out of her character!), 7.7 (hey, let's totally trust Cersei to send her army up north to help us. That totally seems like something she would do!) and 8.4 (hey, you know I bet if I have a heart to heart with Cersei she will surrender. She's a pretty level headed person!). In all cases, it was obvious to show watchers that Cersei would do what Tryion thinks she will do. So why in the fuck can't Tryion see it? I need an explanation on how he became so fucking dumb. If it was Jaime, I could see him having a blind spot for him, but I don't understand this inexplicable blind spot for Cersei.
Jaime: I actually like the idea of Jaime doing a double-reverse from redeemed to unredeemed, but like Dany, the shift happened way too fast. We needed to see him gradually shift back to his old ways or thoughts. There needed to be some internal conflict. As it is, he just flipped in a heart beat after YEARS of gradually being redeemed. It's just bad writing.
Big crossbows: OK, are these things unstoppable dragon killing machines or not? You can't tell us that in 8.4 they're able snipe an in motion Rhaegal out of the sky with all three shots hitting from over a mile away to none of them hitting Drogon in 8.5. This basically illustrates the whole flaw with the final season. Things happen because the script writers need them to happen. Who cares about logic, physics, reason, character motivation? Just get us to where we need to be.