Yes. - If he's skilled enough. Technically spoken this is (or should be) true.
It is just not allways reasonable in the sense of self-defense.

Ok, this is your point of view.
In the aikido wich was taught to me from the very beginning, this is on the contrary a very important aspect of aiki. Not the only one, but a big one.
And is crucial when talking about kihon waza.

Then what do you do, if uke gives you nothing?
Can you only react? How do you take the initiative?
Do you depend on uke or are you free?

This may be true for the "wide/large/big" and "external" movements.
But you can also deal with resistance by a little rotation of the hand, the angle of the elbow, a small movement of your foot and ...
... not changing the external movement i.e. technique, but just using the "internal" structure" of your body, i.e. staying in the same technique but changing things hardly to see.

To me aiki doesn't only mean to "choose" the "right" technique but also choose the "right way" within a certain technique.

You mean, you think you are not able to do so or you don't like to do so?
We practice this way and learn how apply a specific technique no matter what the resistance is. Exactly this is part of our daily practice. It is not all, but part of our training.