Indeed it's present under the hood, we are operating on a CPU after all, which treats all of RAM as one giant shared-mutable blob of data. It will always be there, under some abstraction.

The point I'm trying to communicate is that in practice, for various reasons, Rust programs do not use shared mutable access to objects to the same extent that C++ programs do. For example, C++ programs use observers, and dependency injection (the pattern, not the framework) to have member pointers to mutable subsystems, and we just don't often see that in Rust programs. This is the paradigm mismatch I'm highlighting: to rewrite a C++ program in Rust often requires a large paradigm shift. The pain is particularly felt when making them interoperate in a gradual refactoring.

This is IMO one the bigger reasons that big rewrites to new languages fail, and why new languages benefit from being multi-paradigm, so that there's no paradigm mismatch to impede migrations.