Why Does the DM Client Take so Long to Open?

Unfortunately, this is inherent to .NET, the language in which the DM Client is written. This was a design choice by Microsoft and is not something we have control over.

When you first launch the client, it will take a considerable amount of time to open as it downloads the applications you have access to. Subsequent launches may be faster, but be aware that if you are granted permission to access new applications, or if applications are replaced with new versions, they will also need to be downloaded, potentially increasing the time it takes to open the application.