To be fair, parts of my work codebase are touching on 25 years old, and I work for a startup from 2020. The codebases we're building on have roots in the mid 90s, and the platforms they run on didn't support modern C++ standards for a very long time after that.

So anything including "windows.h" isn't really new development then? Sounds like a strange definition.

I'd say that there is a lot of new projects being started with C++, still way more than there are new projects in Rust, at least if you only count serious ones.

GCC is from the 80s, Unreal and Source are both from the 90s, and LLVM and CUDA are from the 2000s.

Yeah, I'd call all of those codebases pretty old at this point.

I mean a lot of these things rely on copying old code. AFAIK a lot of new games in bigger studios start by essentially copying the old engine into a new tree.

Nope. Ex. game developer here. New C++ projects and libraries are started every single day.