There are so many fundamental design, I would say flaws, but let's call them decisions, that to me, make it so you can't "fix" the overall experience or gameplay.
Realistic fixes?
Performance. The PS4 version feels like it's struggling at times when there is nothing going one. Very choppy / sluggish. That frame rate...
Music. Where's the cool electronic music from the first games? We have this generic 'action orchestral' music that sounds like it was pulled from some music library. They could add more electronic score.
Animation / Glitches. Certainly this could be improved and it would be realistic to think that this and the overall performance is at the top of their list.
Lighting. Maybe they can fix the lighting to make it more natural / cinematic?
What they can't fix, sadly, is the horrible writing, bad voice acting and direction, poor pacing, brain-dead AI, mediocre combat and all the rest of the stuff that is bound by design fundamentals and practices.
One thing they might consider is to dial-back how much people talk in the game - like all the combat chatter that is just so lame and sounds so dumb. Sorry, wish I could be more optimistic, but what a letdown this experience has been - and I loved the first three games, problems and all. But this one...