That question is impossible to answer. However, the negation is answerable. "Is the candidate incapable of the essential job function?" Questions like fizz-buzz, et. al. answer that readily.

Put up a job posting on a job board and you'll get hundreds of applications. 90% of those you're going to throw out because the resume doesn't match the job description at all. What does that tell you about the candidate pool? It's an all out assault of candidate spam. You have to employ these sorts of basic filters to even get the number of interviews you do down to a managable number.

What it tells you about the candidate pool may be less than what it tells you about the qualifications for the position. Job requirements in the computer industry routinely include nonsensical requirements (5 years experience in something that's been around 3 years, 2 years experience in each of 8 items for an entry level position, etc.)

This is endemic to the point where applying only for jobs where you fit the job description is a losing strategy.

And even if your own job posting isn't one of those, how is the applicant supposed to know you're one of the few employers who actually means what's in the job description?

This is a good question. However, there is nothing that will tell you this reliably aside from employing the person.

Most people who are smart and get things done will be capable of shipping code, if they can stay motivated. And that’s where having some signal about their interest can help. I want to know if people can inspire their teammates, not just get along, I want to know if they can lead by example, whether they’ll rise quickly, and whether they’ll love it for many years. The essential job functions are just plumbing, the important parts are more than that and aren’t demonstrated by evaluating for narrow, specific job skills.

Look, I don’t in a million years think grinding on Leetcode is some singular answer, or even particularly good. But I don’t see anything wrong with people who are interested doing it, and I also don’t see anything wrong with asking interview questions. I never put a huge weight on such algorithm questions, and there are a dozen other major interview categories. So there’s nothing wrong with asking a few algorithm theory questions, to see the bounds of what people know. I like getting into questions that people don’t know the answer to, whether it opens a conversation about what it means, or whether the candidate has no idea or doesn’t care, that is a small amount of useful signal to me.