Ask HN: Question on Improving a Product

How does one go about adding new feature or improvising a currently used product by 20K DAU. Is there a process which can be followed to come up with feature ideas? Or is it always talk to your customers? Does session recordings help, what to look for in them? Is usability test a way to go? Lot of questions but I'm tasked with improving a simple product with high DAU but less conversion and I feel puzzled at times. Thanks HN for your input.