This depends a lot on your target audience and your product. A technical audience may see behind UI and understand the technical innovation you have made. For a non-technical audience, you can develop the most complex system and they don’t care about it at all if it’s not pretty. If you only have a command-line interface, for them it’s like you haven’t done any work at all.

Also, for many products the UX is the innovation. Because they do things that you could also do with other tools, like Excel, but with your product it’s easier to do. In those cases, the UI is very important.