You can learn from anyone and, actually, everything. It does depend on what you are willing and wanting to learn. Some people seem to know a lot about a lot of different things. I am not one of them! But in the areas I am interested in, I learn primarily from experience, observation and continuos effort. And I can see that what I learn in one area applies to many other areas as well.
With musicians, there oftentimes is a closed-mindedness that can come into play around musical development, thinking you can only learn from someone who plays your instrument or who plays in the stlye you want to emulate. Sometimes a person thinks they can only learn from "the great ones." This, in my mind, is biased learning and, therefore, is a huge hinderance to the learning process.
I can truly say I have learned something from all my students. Either mentally, emotionally, musically, ethically, socially, energetically and more. I also have learned a tremendous amount form other instrumentalists, singers, painters, dancers, poets, plumbers and everyone I can think of--including my amazing parrot!
Someone who teaches has an opportunity to really interact and work with another human being and watch all sorts of different ways people develop. How can each person be taught the same way when they don't learn the same way? In my mind, it is my responsibility to try to keep the integrity of the individual intact while trying to help them in their artistic process and growth.
Learn from all and your days will be very full and rich!
P.S. In the photo, my parrot, Atlantis, is giving me a lesson. I wonder if this is the way I look at my students sometimes? :-)