A product is much more than the software and its reliability. The business side is just as big of a lift. You need to build a business, not just a product. A business includes understanding the value proposition, not just a potential solution in the form of a tool. It includes understanding how the software fits in to the target customer's workflow, and how it provides real value. You need to be able to communicate that value proposition to the customers, investors and your employees, amongst other stakeholders. Later, this transforms into understanding the sales cycle and how to use marketing to grow your users. The business side has always been the hard part. Software was always easy to build. The hard part is knowing what to build that really provides value.