Miles, no disagreement from me. When I started my first company in the early 90s, we built a business out of creating domain-specific languages for customers looking to make custom application development easier and more economical.

We'd work with a customer to understand their problem space and we'd use YACC and LEX to implement a custom grammar for them. Our software would convert programs written in the grammar into C code for compilation and use.

We learned a lot and had a lot of fun---and made a bundle of money when we sold the company.