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…
A cheap tool to build an audience makes sense, absolutely, but this is very nearly the exact opposite of that. How many users is a $10/mo calendar widget only on MacOS and only with Google Calendar really going to attract? It's expensive, and the audience is a subset of a subset of a subset. Got to start somewhere, of course, but this is like the result of a weekend hackathon, not something that a significant audience is going to drop $120/year on.