I've done a few rounds of selecting resumes and interviewing for jobs at my company and there can be pretty wild differences between candidates. Some people just seem like they never stop. They do well in school, have a bunch of personal projects, work a bunch of jobs, and show an interest and drive in what they do. And I'm mostly looking at students for intern roles or recent grads for entry-level engineering roles. Once you start looking to fill more senior positions, work experience can vary even more wildly.

Part of it is how skilled they are at making a resume or CV and spinning everything they've done into the best possible light, or even just remembering/knowing to list all relevant skills. Like a lot of people know excel, but I could only award points to those who listed it on their resume.

Top-tier would be a candidate that matches all of the need to haves and matches most of the like to haves for the position. They've got relevant education, sometimes beyond the minimum requirements. They've got work experience, sometimes decades of it in leadership roles. They might have papers published in their field. They might be names that you've heard of before seeing their resume.

And on the flip side, there's some awful candidates out there that wouldn't be selected even if it means leaving the position vacant for now. Like people who learned something well enough to pass their tests (assuming they aren't just lying outright about having the skill) but can't answer basic practical questions about it. In one interview (remote), the guy obviously had a friend helping him answer questions (you could hear the whispering, it was pretty funny) but even his friend had no clue.