If you make Push do nothing any gunner can just move through Deathstar bridges crouching and the only thing Sith can do to displace them is use Lightning. Crouch is powerful in tight spaces because Sith can't maneuver to get to you. With current FP drains if he manages to do that he will have low FP or you are bad at shooting. Also if he gets knocked back at the end he will either run away or die. By using crouch you are trading the ability to fight gunners effectively for an advantage against Sith.
You have a good point. It's true that current FP drain makes this bullshit slightly more balanced. Keep in mind that these changes
are situational for maps like Deathstar. I rarely have any problems with this on any other map, but, being that Deathstar is one of the most popular maps in the game, its feels like a prominent issue that should be resolved somehow. In my opinion, Force Push should not be applicable to every single gameplay situation (as it is right now). I also think it's ironic when people say "just get better at aiming your gunfire" when on the topic of a force power that can be spammed up to 5 times (with 100 FP), requiring virtually no ability to aim at all.
What can gunners do to displace Sith on Deathstar bridges? Sith can force push just about any explosive you launch at them (besides blobs). Attempting any close range attacks would just result in getting pushed down or sabered (unless you're a melee wookie, but that's a totally different topic).
Sith players can basically just camp in the middle of the bridge, pushing any throwable that comes in their general direction, and pushing down any gunner that attempts to advance. You would need a specific combination of gunner classes to challenge them, which is unfortunately not a realistic scenario in casual gameplay.