I'm not convinced it's that broken, though - at least from the recruiter's perspective. I have no doubt they pick up many candidates - those of us that are more "discerning" as just the collateral damage.
Simply filling those job openings every time does not mean the right fit is found every time.
Again, though, success from whose perspective? If the recruiter gets their commission, it is a success for them.
Maybe success shouldn't be considered success unless the fit is right.