I thought so, too. But nowadays I believe you actually need a product manager. Because if you have stuff that people really want/need, they will actively google for it and find you. The big issue is that your opinion of what the market wants is most certainly wrong. So you need a product manager who will interview prospective customers, analyze the market, and advise you on which product to build. Once you have a value-generating product, marketing will be easy enough that you can outsource it.