Totally agree with your point, and in fact my first programming gig was encapsulating COBOL next to these domain experts. Very generally speaking the edge case

Totally agree with your point, and in fact my first programming gig was encapsulating COBOL next to these domain experts. Very generally speaking the edge cases exist because you are trying to be all things to all people. Rebuilding an existing, predefined service for exactly one use case is straightforward. The tools available are "good enough" to do the job for one person. That person hasn't been building another SaaS, they've been posting well designed documentation on github.