I haven't grown out of metaprogramming at all. I just try and use it only when it's the best option. Usually because it means reducing duplication.

I liked metaprogramming to an extent in C++. I _love_ it in D.

Replace "best option" with "only practical option" and you're good to go.

That may depend on the language you are using.

In Perl, I find metaprogramming to be extremely powerful. I don't go too deep into Class::MOP usually. However, I do find that focusing on tooling before code is usually a net win. This means a lot of work can be done by writing DSL's that use metaprogramming behind the scenes. It works well and has become a common approach for certain kind of things (like object frameworks).

I'm not saying you should never use metaprogramming. Sometimes there is no other (practical) way. But it can be easily abused, often for a little added convenience but a much larger conceptual complexity and additional debugging issues. Why have a well-designed API when you can have a metaprogrammmed mess instead?