Re: People who are never uke
It's about increasing risk levels into a full-blown, uncontrolled confrontation which has nothing to do with current waza. It becomes personal for them. Their approach is when you bend your knees to get power, they'll bend theirs even lower to stop you.
The only time I've been able to really throw one of these people (or so it seemed), is when we were doing jiyu-waza right in front of Sensei, and I used every power-generating trick I know. No human can block in all directions at once. You can feign doing something here to direct their energy and then apply yours over there.
However the dojo rarely does jiyu-waza or anything equally spontaneous, so usually we are stuck in kata which they block.
@Carsten: You're ascribing qualities to our training method which are not accurate. Delivering an attack while on-balance is the standard protocol. Otherwise you wouldn't be able to do anything against a Karate practitioner. Yes, many people in real life can be easily extended to lose their balance by slight distance manipulation, but good Aikido requires centered, and yet connected attacks.
What makes the technique work is not uke already falling over when they reach you, but you being one step ahead of uke in initiative, which can be achieved through either realtime training, or uke understanding that you're simulating realtime training in slow-motion mode. When neither of these things are happening, uke has all the time in the world to withdraw their energy and regain initiative.
The meaning of the initial attack or how it can be utilized in terms of seizing initiative, or being positionally relevant to current waza, is lost.
Rather, you're practicing with "taking down a person in front of you". You're both on equal ground, and they will escalate if you do - at which point the mechanics become VERY similar to a Judo match, and frankly, I've been tempted to do a crappy osoto gari on these people or just punch them in the face to regain initiative, because it is pretty much sparring at that point.
However, sparring is considered "dirty". Thus it's a stupid situation which wastes time. These people should be at Judo if they desire this kind of energy so much. Judo is a lot safer to practice full-force, it was retooled for that purpose specifically. Doing this in Aikido context, they injure each other, and other students.
_Maybe_ their ukemi philosophy is to only allow a very narrow path toward "100% effective technique" that they only understand, and block any "semi-effective" paths, but the result is a complete lack of connected feedback to nage which should let nage know if they're getting "hotter" or "colder".
There's no learning there. No direction toward improvement. Just waste of time.
Hence I'm done with that.