I'm not quite sure how being able to extend syntax is a theoretical problem. It was just a basic example for brevity. There are many more examples of macros t

I'm not quite sure how being able to extend syntax is a theoretical problem. It was just a basic example for brevity. There are many more examples of macros that solve real world problems, such as writing a compiler for an embedded DSL that is tuned to solving your real problem that allows expressivity and brevity that you would never see without the use of macros.