Given that the employer holds almost all the cards in an employment relationship, the most important part of the interview process is for the candidate to decide whether or not they've be happy working for that employer.
The employer needs to make sure the candidate is competent for the job, and, hopefully, whether they'd fit in with their potential colleagues. Since every job is different, an ability to think, learn, and adapt is often more important than some particular technical ability or experience on their CV.
As the article says, the employer needs to avoid anyone who is applying solely because they're desperate for a job.
A good interview should be a pleasurable experience for everyone involved. Whatever the outcome.