WhatsApp is probably one of the most barebones chat apps I've seen so far. It's providing exactly what I need for communicating with people, and nothing more.

I doubt that adding video calls to a chat app requires a featuritis diagnosis.

Try Telegram :) It doesn't have voice or video chat and the clients are open-source. So you can remove these features if it ever becomes popular ;)

> featuritis

Email likely won't be an eventuality in this case.