I think what I dislike the most about the disney stuff is how shallow it is. It's heavy on action and set design, but incredibly light on worldbuilding and character development. At times, it feels more like an old saturday morning cartoon where the good guys win because they're the good guys.
Take the Empire. In the Disney canon, after Episode VI, they suffered loss after loss until a complete defeat 1 year later where they lost practically the entire fleet in a single battle. They then managed to secretly rebuild and then take over the galaxy 30 years later until they were defeated and lost the entire fleet in a single battle. Meanwhile in the Legends timeline, the Empire, under the command of what was left of the Admiralty and high command, continued a long, bloody war with the fledgling New Republic that spanned 20 years before peace was declared. During this, there were also breakaway empires, such as the one under Warlord Zsinj which were also credible threats. And in the end, the Empire survived, and while diminished in territory, remained a military and economic powerhouse in the Galaxy. They even merged with the New Republic for a time during and after the Yuuzhan Vong war becoming the Galactic Federation.
Another thing I disliked was how the Disney stuff basically made all the hero's accomplishments of the original trilogy feel worthless. In Episode 7, Han's a sad, washed up smuggler, Leia's a sad military commander watching everything slowly fall apart, and Luke's a sad, miserable hobo hermit. All their heroics amounted to nothing in the end. Meanwhile at the same point in time in the Legends timeline, Han and Leia are still happily married, Han's a decorated General and War Hero of the New Republic, Leia's still very active in politics, even assuming the role of chancellor for a while, and is a full-fledged Jedi Knight, and Luke had successfully rebuilt the Jedi Order and even has a wife and son.