Just shooting wildly won't always get you past your enemies, as Darth Vader demonstrated by stepping out of nowhere to block a corridor with his Force powers. To take him out, we had to pull levers and deploy explosives at his end of the hall; shooting them a few times removed the corridor's Vader-shaped blockage.
As in the original game, each character who joins your entourage during a level has abilities that are necessary to finishing it. C-3PO, for example, was the only one able to open certain doors (even after we'd "accidentally" shot off his arm and leg, forcing him to hop around comically), while Captain Antilles was able to man a crane and ferry certain characters across chasms.
"Finishing" a level once doesn't mean it's finished, either; to really see everything, you'll need to come back with a customizable team of characters in Free Play mode, which can open up whole new areas. There'll also be several different ways to get through each level, so feel free to be creative.