I think what you're seeing here is endemic of teams of almost entirely junior engineers with insufficient experience (especially in startups), rather than the software engineering space being inordinately large.
Regarding GitHub's seeming rediscovery of the pre-fork model, I too was pretty surprised -- largely because the model was long-since dated by the time they opted for it, as it doesn't scale well on modern multi-core/multi-cpu hardware. This original HN thread on Unicorn had a vibrant discussion on the subject -- the differences of opinion seemed to boil down to experience and subjective biases: http://news.ycombinator.com/item?id=872361
Regarding GitHub's seeming rediscovery of the pre-fork model, I too was pretty surprised -- largely because the model was long-since dated by the time they opted for it, as it doesn't scale well on modern multi-core/multi-cpu hardware. This original HN thread on Unicorn had a vibrant discussion on the subject -- the differences of opinion seemed to boil down to experience and subjective biases: http://news.ycombinator.com/item?id=872361