I might have to disagree here; I do think the constant rush of what goes on in FC does help to make your more aware of your surroundings in general because of the sheer amounts of chaos that happens in certain locations. That general knowledge can be applied to missions really well if you're any bit decent at the game.
As for unlocks, you're right for the most part but I've gotten my roles leveled up which is needed for the higher mods and slotted weapons 1000x faster than if i were to be grinding missions averaging like 10 kills a mission (take into account waiting for opposition as well) as opposed to getting 30-50 kills in a 15 minutes time period