At the businesses where I worked, developers were hired to be productive in taking on workload. Obviously, new people had to be brought up to speed on the exist

At the businesses where I worked, developers were hired to be productive in taking on workload. Obviously, new people had to be brought up to speed on the existing systems before they could fix problems or add features. If we first had to give them technical training for months before they could be trained to understand the existing systems, that would have taken too much time. Even the front-end user and B2B interfaces were large and complex, let alone the arcane and hideously complicated domain-specific business logic - that took years to learn and be proficient working on. If in a job interview I heard the equivalent of "I can learn your UI framework or whatever" there would not be a hire.