At least my experience in the professional world, if the provided reference says anything negative about the interviewee it’s a massive red flag.

Maybe you don’t think that way, but for every position I have ever posted you’ll get at least 100 applicants, and each of them take a massive amount of time to interview and get through the system to hire.

That reference is one more thing that helps. Better yet, it’s great when someone knows someone that you do, because then it’s easy to vouch for them.

Like when it comes to dating, are you going to date a random person that you know nothing about, or go out on a date that your best friend recommends who knows you?