The existence of the cheat codes has nothing to do with my point. Yes, I can cheat my way through FS2. No, I don't particularly want to, because the story is engaging enough to give me the impetus I need to go out there and do things, and the basic gameplay entertaining and challenging enough that I want to be able to do it right.
FS2 gives you the impression that, while your overall contribution does nothing much to affect the story's outcome, your actions are still important on a local scale (Save that transport, Protect that cruiser, Gather Intel about big bad space flea from nowhere).
In Exposition, I know that even locally, my actions matter little to nothing.
You are missing a basic challenge/reward feedback loop here. If I do nothing in a mission, I don't want to go on to the next, I want to be reprimanded for my failure.
Now, Gameplay: In Exposition, at no point does it really feel like you are flying in atmosphere, much less a storm, or a gravity well. The only indication I have that I am not in some awful black-and-grey nebula somewhere in space is my wingman's word for it. I realize that, at the time these missions were created, the features necessary to implement gameplay changes like this wasn't implemented, but it added to the feeling of total underwhelmingness here. The point here is that it is not different enough from standard FS2 gameplay to keep me entertained long enough. TBP, for example, had Glide as a new feature. TVWP introduced ships with an awful lot of inertia. Some alteration of the basic physics might have gone a long way here.