I think there are times when it is advisable to instruct a new learner to learn how to use the transpose button and after learning, make full use of it. After wiping the eggs and tomatoes off my face, I will explain. If you are a middle aged learner, or perhaps a senior citizen learner, you will be able to learn to play much faster by learning everything in the key of "C" and then transposing as necessary. While you would be trying to carry thiings through every key, you could get pretty proficient in the key of "C" and perhaps even start to play for family, church, etc.
Most training material is in the key of "C" so it would not be hard to find material to use as learning tools.
You would learn(key of "C") every lick, every run, every progression, as many relevant chords as needed so that you could play them with your back to the keyboard. Learn all inversions of the chords to a very comfortable level. Then transpose, transpose and transpose. You are not Peter Nero.
Then after you are excellent in the key of "C", venture into other keys as desired and at leisure.
Of course, there are situations where the transpose button should not be used. We are all familiar with those.
