Here the trivial, unthinking preprocessor allows to do a pretty crazy (though very understandable and predictable) thing, which allows to acceptably solve a problem which would take years and a ton of effort to be solved "properly" (with standardization and compiler support).
When programming in C++, where limited compile and type metaprogramming exists, one is constantly hitting the limits and it causes endless frustration. I go through a mini cycle of grief until I give in and use a macro, or an otherwise less elegant implementation.
You're right in that it has taken years (decades, even) to standardise some better alternatives to macros. But even now C++ lacks some of their power.
I have to wonder how much faster alternatives would have been implemented, if macros weren't "good enough" for so many use cases.
With the addition of “constexpr” and “consteval” compile time programming is the same as runtime for many cases. Templates are obtuse for meta programming but usually can get the job done.
The need for macros much less common in modern code.
Existing c++ reflection has mostly been done with macros, which you sacrifice readability for by declaring your class with macros instead, and I believe is often a runtime thing anyway. Complex type metaprogramming is possible, sure, but often so obtuse and illegible I'd dare say the preprocessor is a better alternative if it works.