I'd imagine they would require some hands-on guidance to create more meaningful abstractions and DSLs for humans.

Call it "vibe coding by tiller". Ha.

Also, I think of metalinguistic abstraction as something deeper than macros. At least not limited to macros:

"An important advantage of making the evaluator accessible as a Lisp program is that we can implement alternative evaluation rules by describing these as modifications to the evaluator program."

https://sarabander.github.io/sicp/html/Chapter-4.xhtml