The C macro language is technically a different language (though today they are specified together, they originated once as different compiler tools) than C and

The C macro language is technically a different language (though today they are specified together, they originated once as different compiler tools) than C and lot of DSLs get written in it because C programmers are trying to avoid actually writing C. There's also a lot of C programmers that prefer to use C++ compilers in C++ mode for their C code to avoid direct contact with C specification bugs or some C standard libraries. (Plus, early C itself was designed to avoid direct contact with Assembly languages which was designed to avoid direct contact with Machine languages some of which were designed to avoid direct contact with Microcode languages most of which were designed to avoid direct contact with TTL logic and TTL logic was designed to avoid direct contact with the useful properties of transistors for computation and so forth. Programming is turtles all the way down.) (Also there are quibbles to be made about "at all costs". JSX is still a superset of JS syntax with a little bit extra added in. Typescript is built to be a superset of JS syntax. You can't write either without a lot of direct contact with JS. Neither seems like "at all costs" avoidance to me.)