This is the holy grail for many content strategists, with the often-quixotic desire to completely throw out all the content that exists and start from scratch. Even if there are dragons of bad content that need to be slain, it's rare that you can delete all the content and start totally from scratch. This is because usually there are large swaths of reference content (perhaps for specialist audiences) that need to remain and would not be worth rewriting regardless (product details, reference research, older product support materials, etc).
Putting aside the emotional impulse to rewrite everything, writing brand new content does often make sense. But virtually always the best approach is a blend of dispositions. Common dispositions that combine with brand new content are: delete (if you are going to start new content with completely new eyes without referencing existing content), variants of rewriting content, variants of automatically moving/transforming content, and integrating with existing source systems.