usually, code generation is preferable to metaprogramming, mostly because it is easier to understand and maintain
To maintain the code, you have to understand the input language to the code generator and its metaprogramming constructs. You're no better off in that regard.
The grandparent comment is saying that if you don't give people metaprogramming built-in, they will resort to outboard metaprogramming.
I.e. you can't stop people from metaprogramming.
macros are programs written in a separate, unique, often turing-complete meta-language, which is implemented entirely in the compile phase of the language which supports them
they're in no way equivalent