Okay, so here are my picks:

The sheer amount of cataclysmic events and wars that follow RoTJ. Seriously, it’s like Luke, Han, Leia, and Lando just can’t catch a break. Every 2 years something insane happens and of course they’re the ones that have to fix it. They never get to retire or live out their happy ending. I don’t have an issue with new conflicts starting up, but do they always have to be so intense and involve the same ten people? This is why I’m very picky with my post RotJ content, and why I prefer to just go by head-canon.
“Never tell me the odds” is apparently some sort of Correllian belief or something? Seriously? Not only does it subtract from Han’s uniqueness, its just stupid.
I dislike how the Fate of the Jedi series turns “the Ones” from the Clone Wars Mortis episodes into mere celestials. I always thought there was something much more spiritual and psychological with those characters and their planet. But no, now all the mystery surrounding them is gone and they’ve been reduced to some overpowered superhero villains.
Also, why is there a need to overexplain almost everything? I get that a great deal of EU lore stems from the old West End Games RPG where it made sense to explain certain things seen on screen, but still. The EU as a whole goes too far with this.
Vitiate is terrible. Way too overpowered and boring. Also, I’m not the biggest fan of KOTOR and that era, but having Vitiate be the reason Revan and Malak turn to the Dark Side is stupid. Completely removes any sense of agency and choice those characters had in their decisions.