This is the case at most companies. It's rather ironic that the interview can be a brain-wracking exercise in futility and problems that will never be encounter

This is the case at most companies. It's rather ironic that the interview can be a brain-wracking exercise in futility and problems that will never be encountered or dealt with on the job. The fact that the two are generally unrelated does lead to both bad candidates being hired and good ones pass up. I assume this is what people mean when they say they are not "smart enough" to pass an interview with Google or another company (unless they really do think they're not smart enough and somehow their job is incredibly tougher at Google than somewhere else). They don't want to play the interview game and may not actually know a lot of the answers and tricks of the game which leads them to think they are not smart enough to work at Google when they're just not experienced in the interview game.