But there is just no magic bullet. If we want to be able to do these things we still need to cultivate the mindset of being a bushi on a street corner in Osaka or something circa the late 1500s, watching two exponents of unfamiliar ryuha engage. How good we can be is defined by how much we can observe, analyze, and synthesize from what we see.
(Yeah yeah and then we need to develop the skill of figuring out why we're not getting inside our sempai's energy field rather than making the same mistake twelve times in a row too.)
You are right that there is no magic bullet. Even with the best explanation in the world, there simply is no substitute for practice, practice, practice.
However, the point of putting together systematic, principle based instruction is to keep people from spending years doing thousands of repetitions wrong. Every time you do a technique, you are imprinting something in your mind and body. It is far harder to change that imprinting, once done, than it is to imprint it right in the first place.
You and I have worked together a number of times. I have explained the technique and you have done it successfully. But that didn't mean you could duplicate it when I wasn't offering the step by step explanation. That's because the outline of the principles still isn't totally clear in your head. So, like everybody else, you catch it and then lose it and then catch it again.
Once the sequence of actions in any technique are clear to you, you will still miss it at times until you have made those principles your default setting rather than something you have to think about. Then you will still miss it as you keep upping the intensity of the training and trying to apply the principles in more varied contexts. Then you die... oh, well. Perfection is a motivation, not a goal you attain.
The most important thing about principle based instruction is that it allows you to become your own teacher. If something goes wrong, you are able to "reverse engineer" and figure out what went wrong and change it. You don't have to sit there waiting for some teacher to tell you. This is also what is required to be able to "see" when presented with the opportunity to train with really high level people. If you do not understand what is going on, you won't even see what is important about what they are doing. Ikeda Sensei barely moves at times and his partner falls down. I can assure you that everything you and I have talked about when we have trained is operating there but your chance of seeing it if you didn't know what you were looking at is remote at best.
In a way, that is really what I am doing. I am trying to train people's "eye" so that they can see. I can't do their Aikido for them... I have enough trouble working on this stuff myself. But if I can help people understand what is really happening in the "aiki" interaction, then they can then benefit from training with all of these amazing teachers we have access to; instead of repeatedly going off to seminars and at the end having no more idea of what was happening than when they arrived.