in most compiled languages you need something like them to get fully featured metaprogramming. It's not necessarily a case of liking them so much as they often become the best option. (note that C macros are a terrible implementation of macros, and yet despite that and the C++ committee hating them with a passion they are still often the only way to do certain things in C++, because the C++ committee has not sought to make better macros but attempt to extend other language features to accommodate some of their use cases.).
Code generation is just external macros; it's the same thing in a worse form.
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.
code generators are programs written in an existing programming language, which produce target language source code as output
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
