I've got about 15 years of experience in software engineering, and have worked for a handful of employers at this point. I've done my fair share of interviews at this point as well. Like many software engineers, I've interviewed with larger companies like Google for potential roles. I've interviewed there multiple times over the years, and have not received an offer yet. But about once every 1.5 years they always seem to call me back and I always get curious again. They no longer have me do the phone screen at this point, just come in for another try.
This last time I had no trouble with any of the questions, but received a flighty response that I "could have answered faster", and a casual dismissal. My only thought was how I could make my hand write the answers faster next time. The reasoning is usually similar to this, providing little insight, as expected.
At what point does this process fail to be effective anymore? If they did not offer me a role the last few times, is it likely they will discover something new in the future? Their recruiting system is a bit of a machine, and I wonder if they are more interested in keeping the pipeline full than providing a meaningful interview process to a candidate. They don't like me enough to hire, but they like me enough to keep interviewing. As a candidate, is it worthwhile to bother with these large tech company interviews that seem to have odds similar to the lottery, and so many qualified candidates that the selectivity becomes absurd?