Changing the Skin does not effect Addons only the interface and layout.
The default Kodi 17-17.6 Skin is called Estuary but there are many more to choose from including the old default Confluence.
Kodi 16 and previous versions used Confluence as the default interface and can be easily set back up with it.
Confluence is a simple interface with a bar in the middle of the screen with the many Kodi sections to select from.
It is easy to change the Skin to Confluence with many more Skins available to choose from such as Aeon Nox and Xconfluence.
Steps to Change Kodi 17 Krypton Estuary Skin to the Old Kodi 16 Jarvis Confluence
1… Click the System Icon at the top left
2… Click Interface Settings
3… Click Skin
4… Click Estuary
5… A box will come up click Get More
6… Scroll down find Confluence and select it
7… It will download install and ask if you want to keep the changes click YES.
The Skin will now be changed to the old Kodi Jarvis Confluence look and feel.
To change it back to Estuary go to System–>Settings–>Interface–Skin.