I think it is definitely as important, or even more important than many other required school subjects. Music is pure creativity. Being creative is what sets people apart from everyday folks who just follow orders from another person. Without creativity we would never have progress.
Music also teaches discipline, such as practicing and practicing until you master a piece you never thought you could play. This applies to school subjects too, where you feel you can't master it, but using the same music disciplines, learning,anything is possible.
Music also teaches us patterns. The early Greeks thousands of years ago knew this and made it required for all students in school along with other standard courses. If you can understand and see the repeating patterns in music, you can understand the world better, which is often nothing but simple patterns, like how we are made of simple cells that repeat billions of time, or things in history that usually repeat.
Very smart people, like Albert Einstein, played musical instruments. Einstein loved the violin. When you are full of creativity, music helps you become even more creative.
