Since the interview process doesn't include any sort of personal question or assessments other than one's ability to memorize algorithms and such, How do you measure "culture fit"?
Culture fit is judged by the candidates personality. Some of the signs of bad culture fit are arrogance, lack of curiosity, or a combative attitude. These kinds of traits usually becomes apparent during general conversation in the interview.
I haven't seen Google worse than similar companies on that front. Interviewing is stressful for everyone. Remember that Google hires engineers and makes them interview. It doesn't hire people for interviewing talent. (But they probably should choose an train interviewers more carefully, and so should the rest is of the industry. )
> Since the interview process doesn't include any sort of personal question or assessments other than one's ability to memorize algorithms and such, How do you measure "culture fit"?
It's very subjective and falls clearly in the category of "You recognize it when you see it".
Typical example of a hiring committee deliberation at Google: "He didn't find the optimal solution but he looked very excited about the problem when he was trying to solve it".
Enthusiasm, interest, being personable, excitement about solving problems, all these things count when you interview, especially at Google.
