Obviously, you need to have safeguards against discrimination. However, you also need to give hiring managers leeway to go with their instincts. Often when interviewing someone you'll have a gut feeling about them, sometimes good, sometimes bad.

Those times when I've had a bad gut feeling about a candidate and ignored it, I've later come to regret it.

If managers can't have discretion without consulting a decision matrix, lest they be accused of some "ism", you might as well just get rid of the interview process and save both the applicants and the interviewers a lot of time and stress.