The responses vary among:
1. This guy is incompetent and should be fired (fairness seeking).
2. This guy is incompetent and will be fired anyway (realism).
3. This guy is incompetent and you should help him to acquire the skills he needs for his job (compassion).
4. Talk to your manager (practical).
5. It depends on the organization and culture (consultant speak).
In general the correct answer is to address any concerns with your immediate manager, while being willing and able to offer suggestions should he/she request them.
Incompetent new employee-should I advise HR/ethics? – Best Practices – Spiceworks