To clarify, what we mean by simplicity is making databases as simple to work with as using an API. An example of this is native GraphQL support within FaunaDB.
We're continuing to make our database concepts like Collections easier to use and understand. I've made a note to clarify the blog post you are referencing.
Collections come from a NoSQL approach, and allow users to change what's stored in data records over time. We see this as a convenient way to store data, without having to worry about specifying a schema upfront that may change over time.