I just wanted to add, there are a lot of Hugo themes but most of them are blog templates. In fact there are very few examples of building anything else with most static site generators.
Serif has an architecture that would allow you to build out a full marketing/startup/brochure type site. Multiple "content types" in a sense. Plenty of working code examples that show list views, teasers and single page views etc.
In my opinion this is why this theme is valuable for anyone looking to use Hugo for their next project.