Nobody knows.
Seriously.
My wife does this kind of work for a living, and based on observing her over the last few years, I think you're wrong
She'd agree that no process is perfect, but point out that there are ways to identify the needs of the team (both skills and personality), and train the engineers to interview in a way that addresses those needs.
I've watched repeatedly (from afar) as she's gone to a new team of engineers, helped them figure out what they really need (sometimes subtly different from what they think they need), and taught them to interview in a way that tells them if the candidate fills that need (and gives the candidate a job he/she is psyched about).
Software engineers are good at building software, hence the title. They're not "interview specialists", which is why in many cases, they interview for the wrong things. Being able to code a bubblesort and steering a team of ninja coders don't have much to do with each other. But not knowing how to interview can lead you to assume that knowing coding fundamentals is what's important, when instead it tells the candidate that you have no idea who you're trying to hire.
Anyway, her job is to teach the coders how to screen and interview effectively and efficiently. As best I can tell, her teams end up loving her for it, after an initial period of growth pains. She's used to major resistance at the beginning. If I remember right, her goal is that when she's done, 9 of 10 interviews turn into job offers, because the team screens out unsuitable candidates long before the physical interview stage.
Now, how to find a recruiter that can teach engineers to interview, I don't know. I hear that a lot of them just forward a bunch of resumes and see what sticks and claim their commission. Like anything else, you have to do your homework when hiring your recruiter. My wife has a small-but-solid number of people whose recruiting work she respects, so if you are a person frustrated by the hiring process, I can connect you (hopefully that comes across as intended -- relevant info to help solve a problem, not as a sales pitch).
Let's organize this thing and take all the fun out of it.