I love Game of Thrones all of the seasons. The last two season where not that bad not even close. I know that D&D get all the blame but the reality of it is HBO shares the blame if not all of it. When it was announced right before season 6 that season 7 and 8 would be the final two seasons. That could only happen if HBO agreed. HBO could have let D&D walk away and brought in new executive producers to take over and even more seasons. However HBO decided to go along with it. To be honest I can't say I blame them. They where pour a crap ton of money in to that show.
The Average Show cost 250,000 to 1,000,000 dollars per ep. Game of Thrones cost 6 million per ep. The last season was 15 million per ep. That is a ton of money. So HBO probably wasn't massively motivated to keep the show going. At the end of the day HBO has the final say not the executive producers.
As for the last two season they could been better but they weren't has horrible as many people make out to be. Everything that happens in the final two seasons makes sense and fit if you pay attention to the show.
There's no excuse for "She kind of forgot about the Iron Fleet" or "killing all of the Dothraki," oops they respawned. That is peak bad writing and storytelling.
To be fair she had a lot going on and she riding a dragon with a lot of things going on around her. So yea it could be very easy to for get about the Iron Fleet. But please share you infinite wisdom as you have tons of experience riding dragons in middle of a conflict.
As for the Dothraki, your making the assumption that all the Dothraki where killed off at winterfell fighting the undead. However she could have divided the Dothraki up and hand moved part of that army some other place. There could a thousand and one reasons why she still had a Dothraki Army at battle for Kings Landing. Your basically over thinking it and making assumptions. Now maybe it need scene to explain that she was going not use the entire Dothraki and Unsullied and had movied them to another location as fall back. Either way it's easy to explain off.
The bottom line is it wasn't as bad as every one makes it out to be. yes could been better think that last two season should have gotten a full 10 ep but it didn't.
Last point I'm gone make and then Ill shut up. They could easily kept the depth of the writing up all way to the very end and then just left the show hanging with no resolution. Every one would been really pissed even more about that then they way they ended it. That is all I'll say on matter.