Why your HR depends on third party recruiter (so-called headhunter, consultancy), does it mean that your recruitment team is not enough capable?

For executive and senior jobs, there are no tests and lengthy interviews, so you need someone well connected and experienced in locating those qualities within a short period of time. Also, personal communication skills can either build your reputation or destroys it as a company, when contacting a rival company CEO to offer him a job in your company. Things like this a headhunter can eliminate.