The situation has improved a little bit over the last few months but LLMs are still only barely usable in languages like C/C++/Zig - and it's not about prompting. I would say that LLMs are usable for JS/Python and while the code is not always what I'd write myself, it can be used and improved later (unless you are working on perf-sensitive JS app, then it's useless again).

And it might be also something with GC, because I suppose the big boys are doing some GRPO over synthetically generated/altered source code (I would!) but obviously doing that in C++ is much more challenging - and I'd expect Rust to be straight impossible.