This is really good advice. Writing a language you'd actually like to use is difficult. It's been a richer source of interesting subproblems than any other I've

This is really good advice. Writing a language you'd actually like to use is difficult. It's been a richer source of interesting subproblems than any other I've found. If it's for education or entertainment, all good. If it's something you're going to quit a day job to pursue in the hope it'll make you wealthy later, quite high risk. Language classifications normally antagonise people and tagging Lisp as essentially COBOL is well chosen for that. You're missing the prolog family and proof languages (coq/isabelle/lean etc). Also smalltalk (from which one might draw self and javascript). Knowing exactly what one has rejected about existing languages is useful as a guide.