The importance of a problem (also called its scale) is the value of solving it. Together with tractability and neglectedness, importance is one of the three factors in the ITN framework.
Todd, Ben (2013) A framework for strategically selecting a cause, 80,000 Hours, December 19.
ITN framework | neglectedness | tractability
Ord, Toby (2020) The Precipice: Existential Risk and the Future of Humanity, London: Bloomsbury Publishing, p. 181.