For one company, I got the list of the most critical roles (directors, security, etc.) and filled all but one role in ~3 months. Filling your most critical roles is obviously high leverage, but companies pay recruiters a tiny fraction of what engineers get paid and then get the expected results.
At one company, I asked why managers found recruiters to be so poor and good recruiters all got promoted into management. You'd never run eng that way, but apparently you'd run recruiting that way.