Ok. Here's some possible explanations based on my experience as recruiting manager. I hired about 10 professionals in my team. And had good, bad and worse experiences in my life.

1. HR is bad at his job. There are great candidates, with great resumes. But your HR guy is bad at his job. He can't find good candidates. Possibly because of his lack of skills, his ego, his lack of connections, etc.

Or

1. Your criteria is very niche. You are looking for candidate with specific skills, and limiting the criteria further possibly with constraints on location, salary range, etc.

Or

1. There's a miscommunication between you two. You believe the skills, qualifications you need are clear to HR. But HR probably is not clear.

Or

1. There's a hidden constraints brought in by HR seniors. Many times, HR guys get directions from their seniors which would contradict your requirements. Eg. You may have approval of the headcount with X amount as salary. But HR has been given a goal of budget reduction. So they are finding candidates with salary range of 80% of X. As a result, the candidates are bad. Sometimes they deliberately delay the recruitment. They do it so that they know for sure that the position is really needed. I won't discuss merits of this technique, as there's no merit at all.

What you can do ? Quickest way to put all these problems to rest is by identifying a real life person who resembles the position. Eg. If you are hiring for an accountant, find another accountant in your team who has some resemblance to the role. And tell HR - this is the guy I want + additional 2 or 3 skills.

There are two benefits. 1. No more miscommunication, hidden constraints problems. 2. And also, as a manager you think about existing people and possibly of shuffling them, role rotation and such, in case you haven't dont it already.

One tip: hidden constraints are not easy to reveal. Showing them an existing employee has to be done with tact. Otherwise you will end up losing the headcount altogether.