The more experience I have the more I answer every question with "it's complicated" and on top of that everyday I am more convinced that methodologies are as vital as they are useless. So useless in fact that here are some of my favourite methodologies condensed into pretty videos to confuse and inspire you even more.
Be aware that most of the time you will only design objects and you probably are not going to redesign the business model but you might and have valid criticism if you know what systems are built of.
This sounds great to un-convinced clients who lived under a rock for the last ten years. In practice, take this as an aspirational model and apply what you can in your daily practice. It is hard to iterate in real life.
You are not designing a full business in one go but keep an eye on the big picture to do really good work. Be aware and be humble... or set your aim high? both? Be wise!