> improvements, not maintenance, drive careers forward.

Google puts a piece of software on death roll by declaring them “in maintenance mode”, that's the state where no matter how difficult it was to work with, and how valuable are the improvements made to the software, the results carries “negative” weight in perf review.

That is, one who devote considerable time on a software in maintenance mode is considered working in conflict with the norm, and should be taught to behave more correctly, and sometimes punished for consistent effort of not reverting that behavior.