The Dragonriders of Pern series by Anne McCaffrey. When I was a kid I
loved those books. I spent months and months tracking down all the books through my county's library system. What kid doesn't think dragons are awesome? Especially friendly telepathic ones you can ride and who can teleport. I remember crying at the end of All the Weyrs of Pern, both because of a major character dying and because the story had obviously reached a cathartic conclusion. Surely there would be no more books after this, I thought.
Oh, how wrong (and naive) I was.
In my early twenties I found out McCaffrey had in fact continued the main series and also added a prequel series, so I decided to reread a few books to refresh my memory and then start on the new ones. The more I read, the more problems I noticed. First, a lot of characters came off as exceptionally flat and stereotypical. Especially the antagonists; everyone who opposed the could-do-no-wrong main protagonists were all uniformly short-sighted, selfish, and one dimensional--and also sometimes rapey and/or abusive in the bargain, just in case you weren't sure you were supposed to not like them. As a kid this hadn't bothered me because DRAGONS, but as an adult it kept me from engaging or caring about the characters.
I also realized McCaffrey had been absolutely shit at maintaining her own continuity, a problem that became more noticeable with each book. I'm not just talking retcons (though there were several of those); she would just seemingly straight up
forget what she'd written in a previous book. She'd make references to events in other books that would be flat out wrong, screw up her timelines, change the personalities of characters, forget about powers she'd given characters, forget about side characters she'd established and drop new ones in the same positions/locations in the story, etc. Since I was binging the books in order, I started to notice this more and more while my memories of the previous books were still fresh, and it became increasingly jarring and took me out of the story.
On top of that, McCaffrey had some very...
strange ideas about certain subjects. Not only ideas that didn't age well (though there are absolutely some of those too), but ideas that were bizarre even for the time period she was writing in. Rape was one of them--particularly how any straight man could be literally
converted to being an effeminate gay fuckboi via violent surprise buttsex. (Not a joke or exaggeration. The
tent peg story became pretty infamous in fandom circles.) As an innocent kid none of that weirdness stuck in my memory, which made me go "Wait, what, I don't remember
that part!" more than once during the reread.
In the end I couldn't make it more than a few chapters into the prequel series, and I haven't been the slightest bit tempted to pick up any work by that author since.