What's aged best here isn't "make DSLs" — plenty of people preach that — it's that they treat tooling for the new language as first-class: error messages phrased in terms of the DSL, not the host. That's exactly where most in-house DSLs die. Anyone can grow a macro layer in a weekend; almost nobody follows through on the debugging story, so six months later you have a bespoke language with stack traces that leak the implementation and one person who understands it.