>Executing code at compile-time is a great idea in general

Well, it did create a big mess and overhead in C++ for one (not to mention adding another turing-complete language on top of it)...

Ah but that's an implementation and design choice issue. It's like saying "classes are a bad idea because implementing them in pure C is cumbersome".

Well, to criticize something people start (and, often, end) on concrete examples they've seen it in practice. And for "compile time code generation" C++ templates are an example they'd be familiar with (perhaps the canonical one, as more people know C++ than Lisp).