I'm not bothered about 'tidy', all loose ends tied up endings, but lazy writing drives me crazy.
Some of the inconsistencies in The Night Manager annoyed me - in the novel it's more than ten years since the main character has worked at the Cairo hotel, so there's at least a better chance of him not being recognised by staff when he returns as an obviously rich and important guest under a different name. In the series, it all happens within a year or two, and still only the nice chef recognises him, out of all the staff of a big hotel that he'd regularly have been dealing with as a night manager? Hmm.
And don't start me on the bad writing in Downton Abbey. Any time a character had a storyline, they would develop and change, understandably, but as soon as their specific storyline finished and the focus was on someone else, that other character would immediately snap back to being the same two-dimensional stereotype they were before their storyline.
You nearly got whiplash from snapping back and forth between Thomas the motivlelessly-malignant Iago figure and Thomas the tormented-but-essentially-decent closeted gay man, Lady Mary the cold, sneery bitch whose only emotion was a raised eyebrow, and Lady Mary the widow who was frightened of loving again and who was anachronistically kind and sisterly to her servants when they got accused of murder or had a baby in her bed. Not to mention Robert the stuffy middle-aged aristocrat vs Robert the sensitive new man, Cora the gurning airhead vs Cora the dissatisfied wife briefly swept away by someone paying her attention and committed to reinventing the local hospital etc etc.
And don't even get me started on why a series would cast two very similar-looking actors as Lady Mary's suitors and not give them any discernible distinguishing characteristics over the course of an entire season or more. I know one of them boffed her in a Liverpool hotel room and the other didn't but I've honestly forgotten which. 