Source: https://docs.microsoft.com/en-us/dynamics365/customer-engagement/admin/about-unified-interface

Microsoft Dynamics 365 is a leading CRM package, and its web interface packs a great deal of power and flexibility.  But what if you don't like they way that it looks, or you want to streamline it a bit for some users or functions?

Although it may not be apparent to first time users, there are several interfaces to Dynamics 365 at your fingertips that do not require any coding or development.

  1. Using the form editor, you can create form variations. This allows users to see only fields that they need and to change the field order where appropriate.  You can do this for mobile forms as well as forms to be accessed with a PC or Mac. 
  2. If you don't like the way that Dynamics dashboards look, PowerBI dashboards provides quite different dashboard experience which may be desirable for some users https://www.youtube.com/watch?v=Z7AAujMPEcw
  3. Microsoft offers several mobile apps for Dynamics, all of which are available at no extra charge.  https://www.youtube.com/watch?v=TWrnSUiZry0  Third party mobile apps for Dynamics are also available. 
  4. Microsoft has two options for using Outlook with Dynamics, the add-in and the app.
The upcoming version of Dynamics has more interface changes in store.  Microsoft is rolling out the Unified Interface across the product.  Here is a sample: https://www.youtube.com/watch?v=6-6im7Cf4XE and an article: https://docs.microsoft.com/en-us/dynamics365/customer-engagement/admin/about-unified-interface for more information. 

If you are willing to do some development, you can use the Dynamics Portal to create a completely original interface to Dynamics data, and use Flow to automate workflows and connect with other products such as SharePoint or even Salesforce as well.