Does this blame shifting really happen though? I've never seen recruiters get blamed for a bad hire. I've seen them get blamed for sending people that fail at the first interview though.
A bad hire isn't on a recruiter unless they are basically lying to the employer about the hire's credentials or background, and even then it's the employer's job to vet what is being said.
Companies are stupid. Recruiters talk them into bad hires all the time, then there candidate gets a job, experience, and they get to replace them the following year, placing another person with the original company and moving the other candidate to the next.
That's assuming the employer has infinite time and resources to interview and vet candidates. They don't, they are overwhelmed, and it's supposedly the recruiters job to make it easier, yet most seem completely clueless and useless.
I said bad "hire", not bad "interview" - this was by design. If a company makes a bad hire, it's not (generally) because the candidate was presented, but rather a flaw in their interview and vetting process. The "how" of the candidate appearing is mostly irrelevant at that point.
I’ve only seen the blame shifting work at another layer: HR dept telling us that they made their best by engaging a recruiting firm, they can do us a favor by finding other recruiters, but it’s not on them if all the candidates we get sent are mismatched.