7 was good at setting up the new cast, though it was pretty shallow. Most people seemed to like Finn, Poe, and Kylo. Rey was criticized for being a Mary Sue, but still wasn't hated. She was trying to get training, and they hadn't explained who she was yet, so there was lots of potential. The greatest Jedi master of all time was alone on an island with the first Jedi Temple, possibly researching the force in ways we've never imagined.
8 needed to do the heavy lifting in terms of world building, and because it did the opposite, the entire trilogy fell apart like a house of cards. It needed to explain who Snoke was, why Kylo Ren was evil, where the First Order came from, and what Luke was doing. It held basically the entire plotline of the whole trilogy, and decided to purposefully tear it all down as an exercise in subversion and minimalism. Snoke was no one. Rey was no one. The First Order was nothing. The republic was 15 people in a small ship. Kylo was evil just because Luke was an asshole. Luke was a loser hiding out doing nothing, and not even using the force - just drinking milk and fucking around. The entire legacy of the previous 7 Skywalker films fizzled out into nothing, representing nothing.
9 then tried to bandage all the worst offenses while telling the story of 3 films in the first hour, and then attempting to bookend the previous 8 in the last 20 minutes. It was a Frankenstein abomination.