One app that I use a lot that I feel like requires some work would be Apple’s default Mail application. Email is essential to our daily lives, and and app that is opened multiple times a day should have both a great user interface and user experience.
The mail app is not half bad, but it could definitely be easier to navigate. As of now, there are two ways to access the email of a particular account. You can click on the account in the “Inbox” section and access the account’s inbox, or you can click in the actual “Accounts” section to access the entire account’s email. This includes the sent, outbox, junk, and spam folders.
Apple should redesign the application with a certain hierarchy so that it is easily navigable. Each account button should access the entirely of that account, not just the inbox. There should only be one way to do things, so that users do not get confused when trying to use the application.
I believe that this would be of huge benefit to everybody, except for those who are used to Apple’s current Mail application. People that use it regularly may not particularly like a redesign, because they are used to what already exists.