A dashboard isn't a place to dump every metric you can measure. It's a tool for making decisions — and most dashboards fail because they forget that.
Answer a question
Good data UX starts from the question the user is trying to answer, then shows only what helps. Everything else is clutter that hides the signal.
Hierarchy and calm
Clear hierarchy, restrained color and sensible defaults turn a wall of numbers into something actionable. Calm dashboards get used; noisy ones get ignored.