Seems that your aikido teacher was wrong from day one or you misunderstood him/her about the comment on "Power".
To practice aikido you should not become powerless, actually is all the contrary.
But the kind of power Aikido helps you develop is not muscle power, but structural and mechanical power, which properly used give you advantage over a more muscularly powerful opponent.
What I mean is Aikido's use of structure/mechanics are more "powerful" than muscle/brute force, when properly applied of course.
So, or you misunderstood what your aikido instructor try to say when he/she refer about "power" in aikido, or he/she doesn't know what is he/she's talking about.
Unfortunately, like you many aikidoits misundertand what aikido is about or are taught wrongly.