Everyone says to create a product that is loved (agreed), but how do you get constructive feedback in the early days? I've experienced that many users are unwilling to engage in conversation, they test it and if they don't like it they leave and won't communicate why. Suppose one creates a new Whatsapp-like product, how would one, in practice, go about gathering feedback?
Dirty secret that startup methodologies usually doesn't tell you: it's mostly trial and error. You observe people, you form a hypothesis about what they want, you put something in front of them, and you see if they want it. If they don't, change something. It's not unusual to require dozens to hundreds of iterations before you converge on something folks like.
This is also why founders that are building for themselves have such an advantage: then you do get some signal about exactly what you might need to change, and why you would want it. You've got to know (and accept) yourself pretty well to be able to listen to it, though.