Darkmetroidomega

It's hard to say, in my opinion. Not every composer in the world had formal training, but that doesn't mean it's a bad thing to have. You can compose without much formal training, but when you want to reach out to a certain demographic with your music, it helps to know some of the science behind the popular music and their respective composers in that category. It's also nice to have some theory under the belt and ear training; it's not like they'll change your whole perspective on how you wish to approach composing. If they do, then you just move along with that feeling. There's no downside to it. Honestly, I would say it's important to at least learn how each of the instruments work; imperative if you're planning to have your stuff performed by a live orchestra, etc. Any composer should know the limitations of an instrument when they plan to write music involving it, lest they create something inconceivable to a performer.