Eh..kinda a lot. Where do I begin ?
1 - TLOU part 1 hit all the marks and was a big success as because it was a personal, character driven story in my opinion, not because of its extraordinary plot or revolutionary gameplay. The plot itself wasn't something extraordinary when you look into it (Joel had a mission to transport Ellie to the Flies for the vaccine), so the game decided to take a different approach, decided to not focus on this actual plot that much and more on the personal relationship between Joel, Ellie and the side characters, and the outcome of such relationships. That's why TLOU was so remarkable as a story, because it put the characters and their development as the main spot point, and hence why the ending was so powerful. TLOU2 was basically just a cliched revenge plot with a pretty typical message about "revenge is bad and will feck up your life". All the characters were either under developed or just poorly written, trying so hard to force you to sympathize with them rather than leaving the choice for the player to decide if he should or not. The game just didn't know what made part 1 tick. It wasn't the main plot, it was the writing and development of characters. If you removed this element you will be left with an Ok plot at best which is the problem of part 2 story.
2- Regarding the cliched revenge plot, it all felt forced, as if they had no ideas about how to write a story for the second part then just remembered a - literally - no name, unimportant character in part 1 who appeared for less than few seconds and decided to make his death the main center of the revenge plot of the second game. Like really ? You expect me to sympathize with Abby for the death of her father whom I saw for few seconds in the first game, by trying to show some flashbacks for him and Abby in this one ? Come on. Not to mention that the doctor was actually threatening Joel with his scalpel. This is all follows the same trend of trying to force players to care about characters even if they're underdeveloped, just because the developer wants to, you have to as well.
3- The side characters in this game was bad, like, really poorly written and serve no purpose for the story, neither do they have any emotional impact on the players. Jesse and Dina were pointless characters, cut them and you won't miss anything. I legit didn't give a shit
when Jesse was killed. He was barely even in the story for me to care about him.. Compare this to Sam and Henry in part 1, their relationship with Joel and Ellie and how their story unfolded and got concluded, and how it had a heavy impact on the player, in comparison to Dina and Jesse's plot lines. This is another point of how the second part just didn't understand what made the first part great. It wasn't the main plot, it was the characters and their relationships.
4- The Abby section was really a drag in terms of the story and the direction was terrible. It's the epitome example of the game trying so hard to force me to care for he when I really couldn't. The game cuts the story at its climax when Ellie and Abby face each other at the theatre just to set you through a 10 hours of a pointless journey with Abby, her crew and this child, before returning to the same point again, just all a try to mimic Joel and Ellie's journey from the first game, and shows you the similarities between both. The difference is the relationship between Joel and Ellie had a lot of time in the first game to develop naturally, and not just undercooked like Abby and that kid. These 10 hours served nothing bar dragging the story for me. This game suffers a lot from trying to be deep and complex by just painting everyone in grey color and telling you "look, there's no black and white in this world, everyone just fights for their own survival". This point is good when done right, but part 2 overdid it, and it eventually hurt it, and weirdly, contradicts itself a little bit when it tries so hard to force you to believe Joel was mistaken when he saved Ellie instead of letting her be sacrificed, even though he was also doing what's best for himself, like every other one in this world.
5- I honestly have a problem with a certain aspect which isn't mentioned a lot, but I feel this game has a pretty big ludonarrative dissonance problem. Ellie slaughtered ton of people throughout her journey without shedding a tear, has been a survival for years but she got a panic attack because a woman she killed was pregnant ? Like, come on. Considering the fact that, I said above, the game tried a lot to tell you that those people killed by Ellie are actual humans and not just NPCs by making them call each other in horror when their teammates die in an encounter, and Ellie was still slaughtering them without losing her cool, to see her going into a panic attack just because of the pregnancy aspect didn't fit what I was doing in the game. Same for the ending, which as I said at the start, very cliched when it comes to these revenge stories.
6- Joel's death I believe was discussed to death, but I still refuse to believe the man who was shown to be an ultimate survivor with ton of experience in the wildness let himself and his brother go so easily with an unknown group without him shown any concerns during the journey, or even telling his brother to be careful and cautious around them. He didn't even look mad when his brother said his name in front of them, but just followed so causally by saying his name as well. I can expect it from his brother considering he didn't fight in the wild that much but Joel ? The guy should have been warning his brother to take extra caution if they're going to the hideout of an unknown in a world where everyone wants to kill each other.
7- Let's talk about the gameplay a little bit. The game was solid, the gameplay wasn't bad or boring at all, it was mostly an improvement on the mechanics present in part 1, but it missed a lot of opportunities. This game had the potential to be better in gameplay, rather than ending up just an improved version of part 1. The open area at the start of the game was done really well, but then you reach the theatre and you discover that this is literally the only open area with optional content in the game ? I couldn't believe it. Why build such a a great area just for one chapter, then make the rest of the game fully linear ? When I reached the theatre I thought the game will be like a hub area with this theatre as the center of operations, with new areas opening up for me in this open area the more I progress, before turning into linear in the last few hours of the game, but no, the game gives you a nice open area to explore in first chapter then strips it away from you and leaves you with yet another linear experience. I thought Naughty Dog were done with this experience in Uncharted Lost Legacy. I thought they tested it in this game to see the reaction and will go one stop forward in TLOU 2 but unfortunately, they played it pretty safe. Compare this to say, a very recent example which is Resident Evil Village, it gives you a consistent small open are which opens gradually for you as you progress alongside linear segments that cuts the exploration from time to time, or Metro Exodus, which gives you a full small open area in every chapter to explore freely. It was the perfect time for Naughty Dog to take this decision for the entire game, and not just for the first chapter.
8- Abby's section, regardless of it dragging the story and honestly doesn't help the plot in any way imo (Except for forcing you to feel for her because the developer wants so, as I said), has a big problem in the gameplay imo, that Abby is really nothing different from Ellie when it comes to the combat. Abby's weapons were basically a variation of Ellie's. 2 handguns, a different kind of shotgun, a different kind of rifle, a crossbow instead of bow and arrow..etc. Really ? If you're going to make me play full 10 more hours with a new character why not make her having a more unique and unorthodox set of weapons to make these 10 hours different from the first ones ?