My opinion (as a community member and contributor):
PostgreSQL is willing to accept delays in some features -- even if highly desired -- to enable high overall feature development and quality.
Also, more developers are willing to put time into refactoring and simplifying what they need before starting on their project. In other words the groundwork is laid first and then the new feature.
Another thing that might help is that there is no bug tracker. Bugs are fixed and the fixes backported after a report comes in. Bugs don't end up stuck in a backlog.
PostgreSQL is willing to accept delays in some features -- even if highly desired -- to enable high overall feature development and quality.
Also, more developers are willing to put time into refactoring and simplifying what they need before starting on their project. In other words the groundwork is laid first and then the new feature.
Another thing that might help is that there is no bug tracker. Bugs are fixed and the fixes backported after a report comes in. Bugs don't end up stuck in a backlog.