> Domain knowledge can be learnt much quicker than how to apply good engineering principles.

Partially disagree. Broad-strokes domain knowledge can be learned quickly, but honing that domain knowledge with nuance and consideration for complexity, particularly for organisations that are unique and are not often thought of as 'software development houses', can take years if not decades.

Yet I still see (and code review) 'professional' software developers that don't follow good software engineering practice.

> Engineers whose main competitive advantage is domain knowledge are probably not that brilliant at engineering.

The same is also true of engineers without domain knowledge, certainly in my experience. Maybe we just got unlucky...