Perhaps you take the basic features for granted. For example, it works well on a wide variety of devices, especially those with low specs. What about audio quality, which has gradually improved to the point where people I know don't make "normal" calls anymore. What about latency on awful connections. Often when I'm in a place with poor reception, Whatsapp works when other apps don't. All of these aren't build-and-you're-done kind of features. You need to invest continuously to make sure you don't regress.

And the flipside is that people will look at your app and say "what have you done for me lately? What features have you added?"

I have no idea what are these things, and I've never heard of them eventhough I use whatsApp daily. Please.