It is a valid concern. Credibility is important for a startup. It also depends on what you're offering. If it's something remarkable then it won't matter as mu

It is a valid concern. Credibility is important for a startup. It also depends on what you're offering. If it's something remarkable then it won't matter as much. People will just want it and might look past things like design to get it. Usually though when people are opening up their wallets they want to make sure the service is credible and the overall design is the first thing that helps them make this distinction, followed by a blog, founding team descriptions, press mentions etc...