Sure, you don't "have to" but you most likely do. To understand something implies some grasp of scope and size. And if you're continually working on toy proble

Sure, you don't "have to" but you most likely do. To understand something implies some grasp of scope and size. And if you're continually working on toy problems, you'll never encounter problems of the appropriate scope or issues of scale. So that's kind of what people mean when they say you need to work with something complex. To understand a complex system is to know which parts are important and which aren't and at which levels of examination.