Maybe that's true at companies selling to consumers (everyone is a consumer, so everyone can conceviably have valid ideas for new features). However, at companies selling to businesses, the developer is usually more or less clueless about the product domain (even if it's something technical, like CAD or data science) and has no useful ideas. It's the product people who (ideally) have decades of domain experience and talk to users from various companies constantly about what they would like to see added.