Michael, what you say is correct up to a point. My teacher has said that working harder is not effective. One needs to practice and listen to the body. Mental knowledge is helpful to analyze what might be going on, but it is a hindrence when performing Tai Chi itself. The first principle is to relax and relax the whole body including the mind. At that point the mind can be free to listen to the body without interruption of thought.
Practicing single moves is very helpful to understanding the mechanics and energies involved. I have been practicing some of the movements in isolation and find that I can play with the body position and energy involved more intensely. Also, then when doing a set, there is some familiarity when encountering a movement that has been practiced by itself.
The other thing that can help with understanding is to practice at different speeds. From very slow to very fast, always completing each movement. Very slow motion requires some extra attention to every body part's participation in the move. Very fast motion takes some practice to ensure that the body is reacting the same going fast as when going slow, and trying to stay totally relaxed in the process and not use force. By varying the speed of the form in this way, when performed at a "normal" pace, the body remembers better what is required and this frees the mind to listen more clearly. Practice in this way also frees the performance from being "in a rut" when constantly moving at the same pace. This allows the mind to pay more attention to all the parts and joints of the body and enhance the flow of energy.
