I hated Halo 4 and Halo 5's storyline. Spartan Ops was also a disaster. I thought Halo 4's storyline was just as bad as Halo 5 because of how stupid it was. It ended up making me hate Cortana and Chief and how they made their relationship way too important. Not to mention the ridiculous amounts of plotholes. Halo 5's storyline was almost more tolerable because basiacly nothing happened. It was very poorly written and did not greatly affect the universe, while Halo 4 was poorly written and greatly affected the franchise direction. Halo 5 campaign was explained at the end of the first level when Hasley basiacly tells you that Cortana is the villain. The rest of the campaign becomes predictable especially the AI governor character. I mean Halo 5 played better than Halo 4 although again felt like it lacked good setpieces and got worse as the campaign went on...I don't know really I disliked both. Halo Reach was far better in terms of gameplay than the 343 games, but I also did not like that campaign's story. However, to be fair Reach had a much better level direction and focus. I choose to forget 343 campaigns because frankly they don't come close to what Bungie gave us. I would gladly take Halo 2's cliffhanger ending or Halo 3's plotholes because you essentially get both with 343 at a much greater scale and worse result.
Cortnana and Chiefs relationship was made massive ay before 343. Particularly in the books. Its fine if you dont like that, but theres much more to the emotion of Masterchief, Cortana and Halsey than Bungie brought out. 343 have chosen to bring out much more about the UNSC, Oni, the Spartan program and the forerunners. All stuff Bungie didnt remotely touch on.
But these things were always there. After all depending on what you know about Halo Cortana is essentially Dr halseys personality in an AI. The only AI she did this with.
But like I said you dont have to lijke this part of Halo. But it existed as a major part of Halo way before 343.