There is a concept in Japanese that is essential for someone to begin a martial arts journey, or starting a new martial art. This is Shoshin: The Beginners Mind. The reason this concept is so important is it requires a person to approach training as a beginner, so they can learn.
As a sensei, it is very hard to teach someone who doesn't want to be taught. They may want to learn, but don't want to be taught. The unteachable person thinks they can learn on their own, or that what they have already learned is the ultimate thing there is and thus no one can teach them differently.
I'm not sure why they even go to a new dojo with this mindset. Even though I have over two decades of martial arts training, 20 of those years in the Bujinkan, when I visit someone else's dojo, I take the attitude of a beginner. If for no other reason than because it is polite. It's like the proverbial question: What is the best kind of cup? An empty one. One must empty their cup in order to fill it with something new.