This example has nothing to do with your (faulty) assertion that languages do not matter. You'd be far more productive when writing your code generator in Lua than when writing it in assembler. That's because in comparison to assembler, Lua has many more features that help you get the job done. It boggles my mind that you'd even try to claim otherwise.
A programming language doesn't automatically make a specific programmer more or less productive because he/she now has access to language feature 'X' or 'Y'. Software development is about the approach *you* take to ensuring that your code is stable, maintainable, and efficient (where necessary), and in this, fundamentally C++ doesn't save you any time over C/C#/Python/Lisp/ASM/Whatever (I say this as someone who actually uses C++ for most things, and C#/python/lua/mel script/max script for the rest).
I could write a code generator in 5000 lines of lua that spits out 5 million lines of C. That would make me significantly more productive than a programmer who spends 3 months writing 3 million lines of bug ridden C++.
Seriously weird strawman argument. If you have 100% perfect, 100% efficient C code that never needs to be changed again, then sure, you don't want to go in and change it for any reason. But I didn't tell anyone to do that. Rather, I'm saying there are benefits from writing the code in C++ in the first place, even if the code is not object oriented, and even if it mostly looks like C.
Complete and total bullshit. If I have a working piece of C code, it sodding works! Changing the interface (cos references, lambdas, and smart pointers, are cool lolz!), just forces you to: