Literally every time you see a startup release a product that seems trivial it's because that's not the full story. You're judging without complete information. For example, the public face might be a simple Mac calendar widget, but that could be the gateway to calendar sharing, native office apps, meeting booking, event management, ticket sales, corporate flight sales etc. Building an audience with a cheap tool that…
Either way, I don't see the harm in putting it in front of people now, and I see a big downside to either polishing it more, or pivoting without having tested it on people.