People learn in different ways;

Some are visual learners and learn better by observing what you do. I have them watch my fingers while I fly figure 8s, I show them about visual cues while on the ground (eg. alignment of the tail to the wing, visibility of the gear etc.) by positioning their plane and showing them what it looks like in differnt attitudes.

Others are tactile learners. I use the 2 second input/2 second counter input approach with them and have them practice inputs on the ground before flying.

Some are auditory learners, I have them repeat phrases like "I'm in a left turn, RIGHT to straigten up".

Yet others are conceptual thinkers. They need to understand what's going on. I spend more time on the ground discussing aerodynamics, resulting in success.

I've taught many different types over the years and I strongly believe the only ones that CAN "never get it" are those that lack the desire or have special learning disabilities. Unfortunately many other WILL "never get it", simply because their instructor(s) can't reach them.