Any technique can be stopped if uke knows what is coming and nage isn't allowed to hit him.
I don't think that this is true. Maybe it doesn't make sense in a martial way to persue a technique which is blocked by uke.
But I think technically it is possible and is a very good method to learn the essence of a technique, to understand how it works.
And it teaches how ones own body, center, movement, posture has to be used and to be adapted.
For example: In the case of ude kime nage, uke can block a forward movement. If you don't try to throw uke to the front, but lead the contact you have to his blockin elbow straight down, vertically, in most cases uke will collapse.
Another way is moving him by rotating ones arm under his blocking elbow.
Or twisting his wrist a little bit mor like in shiho nage.
There are so many many ways to adapt ones technique to ukes behavior. So I myself think, it is much to be learned through those blocking manouvers of uke.
What do you want to say citing Ueshiba?