For C++, just take lambda captures, you can do [&], [=], [a], [&a], [a = b] (and I probably forgot half), the many way you can do initialization in C++ became a meme, but it really permeates the whole language whose design is driven by enthusiasts and people who have an interest to make it more complex (trainers, book authors, consultants, etc.)

For Rust, I think it is a bit of a different story and it is harder to point to specific features. The language is clearly much better designed (because it was more designed and did not evolve so much) and because of its roots in functional programming. Just overall, the complexity is too high in my opinion and it a bit too idealistic and not pragmatic enough.

For C++ specifically, constructors. Just have functions for gods sake.