While Delve can assist with a visual scan of your recent documents (and other Peoples (that you follow) recent documents (that you have permission to view), it doesn’t assist filtering numerous documents authored by numerous people across the organisation.  Leveraging content classification/metadata/tags, can be powerful when faced with a myriad of documents and you quickly need to filter down to the exact one you are after. This is simply one example of the importance of a good Information Architecture. (But Delve is cool none the less!)