I don't think "opinionated" in the context of a database system means refusing to implement useful features. When I think of unopinionated software, I think of software like Jenkins; it feels like a plugin glue framework that does barely anything useful out-of-the-box and leaves it up to the user to create a working configuration out of the tons of plugins available.
Aside from being immediately useful just as a basic relational data store, my impression of PostgreSQL is that the "opinion" is apparent in the way that new things get done. There seems to be a culture of either implementing things well or not at all, and to avoid rushing things just because people want the new feature right now.
Aside from being immediately useful just as a basic relational data store, my impression of PostgreSQL is that the "opinion" is apparent in the way that new things get done. There seems to be a culture of either implementing things well or not at all, and to avoid rushing things just because people want the new feature right now.