Principles are useful when they compress hard-won experience into portable judgment.
They become harmful when they are treated as badges. Pragmatism has the opposite failure mode: it can mean clear-eyed tradeoffs, or it can become a polite name for short-term drift.
Good engineering needs both. Principles keep local pressure from erasing long-term quality. Pragmatism keeps principles from becoming detached from the work.
The test is simple: can the principle explain what it protects, what it costs, and when it should yield?