Thanks @Paul. Yes indeed, we had a very specific set of skills as requirements for the job. This is because we had some established systems and we needed to continue build new features using the same technologies.

Hiring senior developers who have the required knowledge, skills and experience in those technologies simply means we do not need to "train" them to get started. This in theory would allow us to ship faster and meet deadlines set by shareholders.

Although I agree with your statement about hiring for the experience they bring, I'm not entirely sure that taking anyone who doesn't have the experience in the technologies we're looking for is a good idea.

Having said that, I convinced the company to look for mid-level engineers that we should train to reach that senior role. That's a great motivation for them in their career progression.