Other than maybe pushing the door button with the force, I don’t see what Luke is neglecting to do in the rancor scene.
Is he supposed to fry it with lightning? Choke it to death? Bring the roof down on it? I think it’s easy to believe Luke was doing everything he could and just isn’t powerful enough to do any of those things.
No, it is only that he can do in my opinion (use the force to push the button).
People here seems to think Jedis are gods, that can kill hundreds of people with a single gesture. It is not like that at all, and even if it was, Luke certainly couldn’t do it. He didn’t finish his training and He doesn’t even have a lightsaber ! What would he do if Bobba Fett and all the guards start to shooting him? Wave his hand to deflect all the shooting? Come on! It´s a single man unarmed ! And Jabba faced Jedis before, he knows what they can do. No single Jedi (and without a lightsaber I might add! ) would be able to beat all the guards in Jabba’s palace. And Jabba knows it, so why would he be afraid of Luke? So there’s no need to Luke to hide his powers. As a matter of fact, I think he did everything that he could there.