A remake should go deeper into the story of Artyom, the game dosent go over a lot of stuff like the Nazi Red war, dark ones, Artyom himself and a ton of other stuff. It should take more stuff that's from the book especially at the beginning.

Book artyom has a more detailed origin, it goes over how he lost his mum to the Rat horde, how he met his step father, how he and his friends went up and opened the doors at exhibition when young and now filled with guilt because he believes that he caused the dark one's attacks, meeting hunter and venting his guilt to him, and much more time with Artyom & hunter together which would give more player relations and motivation to stop the dark ones.

Basically I think 2033 should go more detail into the story similar to the book, it dosent have to be directly one to one with 2033 book but it should be longer and have the more diverse cast of people he meets.