Whatsapp is not compatible with iPods which I always found annoying. This is because Whatsapp requires a SIM, which iPods don't support.
Skype nagged me to update, which I couldn't since 5th generation iPods are tied to iOS 9.3.5 forever and can't update. The 7th generation iPods however have a later version of iOS and support more apps.
Currently I have two phones. One is a dumbphone for normal calls and SMS (You would be surprised at how much business is conducted with SMS and calls). Then a smartphone which I NEVER use for calls, just use it as a mini 'tablet' for surfing the web and using Maps etc