Sounds like a one liner intended to boost the self-worth of marketers. There's nothing wrong with what the average marketer does, so no need to make it into something it isn't.
Well, to sell something you need something people want. Finding a market and coming up with a product in the abstract is part of what's traditionally the marketing department's job, even if it's not what the travelling salesman does.
Too many people view marketing as what you do after you've built the product. Any company worth its salt understands that its also crucial before you've built the product.
Perhaps, but it is not untrue. Which is why it's good for developers to know a bit of design/need-finding/marketing, even if you never want to be a "salesman".
As someone who has seen the process of trying to commercialize bleeding edge academic research up close, I can tell you that knowing about your potential users and their needs can save you from building the best possible solution for the slightly wrong problem.
Sounds like a one liner intended to boost the self-worth of marketers. There's nothing wrong with what the average marketer does, so no need to make it into something it isn't.