Is Good enough, good enough ? Do PSLs or RPO for recruitment attract the Best of the Best, or are they a de facto pathway to mediocrity ? by blocking the best talent

Is Good enough, good enough ? Do PSLs or RPO for recruitment attract the Best of the Best, or are they a de facto pathway to mediocrity ? by blocking the best talent.
The best senior people are passive job seekers, the smart ones use recruiters to find their next career move for them, just as really succesful people use house hunters and personal shoppers. They are cash rich, time poor.
So what do PSLs achieve, apart from making the lives of internal recruiters easier ?