This is such a huge problem. It's even worse than it looks: because users are slow to upgrade, changes to the database system take years to percolate down to the 99th percentile user. The decreases the incentive to do certain kinds of innovation. My opinion is that we need to fundamentally change how DBMS are engineered and deployed to support silent in-the-background minor version upgrades, and probably stop doing major version bumps that incorporate breaking changes.