To me, and to a lot of people. Kryptonite hurts Superman. How is him being hurt "not being Superman"? And then the man, despite the presence of Kryptonite and his strength being sapped, manages to LIFT A CONTINENT INTO SPACE after his solar bath. And you tell me Superman is nowhere to be seen in this film?
Powerful, as in emotionally powerful, not as in Superman being powerful in every scenario. Superman didn't "fight back" because he was standing on an island made of Kryptonite, and he was essentially *****slapped, and by the time that was over, it was over regardless. And he did put up a fairly good struggle considering everything he was going through. Wah wah, he didn't throw any punches. Probably had something to do with the fact that he could barely stand after landing on New Krypton and soaking in the K radiation.
And if you don't think that Superman, after being exposed to that much Kryptonite, being beaten, stuck with Kryptonite, and almost drowning and then escaping, knowing he's going to die and going back regardless, soaking up the sun and doing what he does at the movie is somewhat powerful, you should just stop caring about Superman right now, because you don't get the character.
What do you want, powerful emotional moments like "I failed them Alfred. Despite the fact that none of this is my fault, I'm just going to give up right now because my house is on fire"?
Let's see how much of a fight you would put up exposed to an entire island that is composed of a radiation that absolutely drains you of all strength, and then being thrown down a flight of stairs and taking a savage beating. He was essentially mortal at that point.