Racket’s whole schtick is that it allows for language oriented programming. Sure it’s a scheme and it has parenthesis, but a lot of languages in it’s toolkit do not. Not only that when you design a new language the reader converts your new language code into s-expressions and the expander gets it all the way to Racket code. Which is how Rhombus will more than likely work as well. So knowing #lang racket is still a requirement when creating a new language on top of the Racket VM