C++ dev with minimal experience of composition here, but this is a great article and it's something I've been trying to play with more and more. Out of curiosity, does anyone know if there are any known big pitfalls to avoid with composition (thinking of things like the diamond problem)?
The only thing I can think of: you often need to strike a balance between having interfaces that are too generic/large or too specific/small. However, you already have to worry about that in OOP (God Object vs ravioli code) so it's not a huge deal.
Another reply suggested giving Rust a try, and I do second that. But if it's not your cup of tea, at least take a look at some of the standard library traits - std::io::Read/Write and std::iter::Iterator will give you a good idea of what composition can do.