It's not as if Postgres is compromising on quality to add features, they're still very good at keeping Postgres stable even at the impressive rate that new features are added.

And while there are cases where I might agree with the general sentiment, I strongly disagree with this for Postgres. The new features are important and useful. Postgres is not a very specialized tool, it is a general purpose database that is used in many different ways. It isn't just done and feature-complete, there's still a lot of potential to improve it for various use cases.