Racket DSLs aren't the same as 'spinning up a new lexer' at all.
Making DSLs is hard, and being a PLT expert does not make one an expert at language implementation. Those are completely different skills (see Brady's reimplementation of Idris on Chez Scheme and the reason for it).
Racket allows people with new ideas to prototype them efficiently by easily implementing a compiler that would've been an interpreter otherwise.
In my experience most dsls are not of the quality of Typed Racket or Scribble. And many of the good languages designed in Racket could be just as well designed if they targeted LLVM. And for 99% of the programmers I've hired they'd be better spending their time further understanding the existing abstractions and research in the many great languages that already exist rather than halfbaking their own because it's so easy and tempting.
As I said, I like Racket. And I agree with you it's a nice environment for playing with new language ideas. But most of those ideas are bad and are just incidental complexity. And the 1 of 100 languages that are great ideas and needed by the world are better off spun out with their own parser and toolchain without being so tied to Dr Racket and Chez Scheme.
Racket allows people with new ideas to prototype them efficiently by easily implementing a compiler that would've been an interpreter otherwise.