I did contracting in the Silicon Valley for 25 years so I did a lot of interviews. It’s kind of single dimensional in the software industry. You are your skill set. If your 7-10 skills match up with their needs you get a programming test. It’s your job to curate those skills on your own unpaid time. If your skills match and you pass a test you’re 80% there. The tests are setup for you to fail. You have 30-60 minutes to solve some tricky algorithm. If you have seen it before, your in. If you haven’t seen the problem your nerves take over, you can’t think straight and you fail.
The live interviewers are other engineers. Not the best communicators. Somehow you find something in common or not. As in any job interview likeability is the key. That’s your most important goal. People are willing to overlook a few bad answers if they feel they would like to have you around.
Face it interviews and the job search in general is arduous. The employers job is to find holes in your qualifications. You have to anticipate those holes and fill them. You get the job if they have the budget, no guarantee and you happened to be more likeable than the other candidates. Don’t take it personal.