I don't know if I'm going to say what everyone else has already said about this character. But I want to share my thoughts about him
1: the lack of his identity. I thought they were going to bring back custom characters. Mostly because they kept his identity a secret, and the thing I liked about Bell is that Bell could have been whatever you wanted him to be, so I originally thought Case was going to be the same thing. But he wasn't and they brought back the silent protagonist. I feel like there was no need for him to be silent; the text dialogue is fine, but it could have been: first, you pick the text, then Case says what you meant, like in games from Telltale or Fallout. But we didn't get that, which was pretty dumb. And they kept his identity a big secret, especially in the cutscenes and gameplay, which you know is stupid because it wasn't even going to lead up to a big reveal of who he was. I mean… I originally thought John Black Ops was going to be Case in the MP, but I felt like they also wasted that. This is the same flaw they did with Logan from COD Ghosts
2: I don't think they made us care too much about Harrow especially when she was to be a twist villain. I feel like they could have given her a bigger connection to Case, it felt like the twist only mattered to Marshall which is what they led up to in the trailer. It felt like it never mattered to Case whatsoever. I felt like they could have done whatever to make it special, them speaking to each other more when they had the chance, or anything it could have been romantic if they wanted to go that route.
3: Case shouldn't have died. I feel like this isn't fair. At first, when Bell died it honestly kind of makes sense… because he didn't appear in BO2. Just dispose him even though his death is honestly pretty sad after everything you did for them. (I personally have my headcanon where he survived getting shot). But for Case I didn't want them to kill the protagonist just because they were close to BO2, they could have at least have him live. I felt like it was such unnecessary death, I personally believe this also showed they didn't care about his character when creating him and putting him in the story, he mattered so much to the characters in the safe house, and after we cut to them talking to the Livingstone I thought Case was going to turn up somehow alive because the way they acted like they didn't just lose a good friend.
This is what I have to say about him for now. And these thoughts always bothered me, because he could have been one of the best protagonists in the Modern Call of Duty era but they wasted it by having us not care about him. If you have anything to add on or question about what I meant I'll be happy to tell you what I meant.