They're using recruiters wrong. We generally don't use recruiters to
filter candidates, but rather to
find them for jobs where network-based recruiting fails and candidate flow to public postings is poor in terms of volume or quality.
We give them top-level criteria ("mid-level iOS developer", "entry level data scientist"). Any further criteria are very unambiguous and easy to assess in a 5-minute discussion if not off a resume ("has used Python for at least a year in a professional capacity"; "has shipped at least one app to Apples App Store"). They send us a trickle of resumes. We decide which resumes suggest the candidates are qualified enough to phone screen (usually about a third to a half).
For the best of those, we phone screen and issue a simple technical assessment that gives us an idea of the candidate's baseline skills. Then we dive deeper if we need something specialized (e.g. deep knowledge of a specific protocol.)
We also give our recruiters feedback on why we decide not to hire a candidate (e.g. "he seems like he'd need an environment with more structure" or "she knows HTTP like the back of her hand, but we need someone who's used JavaScript since 2003".)
The recruiters use that feedback to inform what other positions they send the candidates resume to. And they use other clients' feedback to help decide who to send to us. Our best recruiter has few enough candidates that she can only send us a few per week for any given position.
But she knows them really well - what they're want for their careers and in terms of process and culture; what other companies have determined are their strengths and weaknesses; where they are in the interview process with other companies and what they think of those companies; and of course, what they think of us.
And she knows us well enough that (for instance) we're one of the first places she'll send a resume for someone who's self-taught and looking to leave the freelance life, and no longer bothers us with the resumes of people with CS PhDs who insist on having a project manager and Gantt charts for everything they do.
If your recruiters are using spray-and-pray and have so many candidates that they have to machine-filter their resumes by keyword instead of knowing their candidates personally, you need to find better recruiters. The ones who get a position description from you and then screen-scrape LinkedIn to "find" "candidates" are just wasting everyone's time.