D has a more unusual take on private fields. Private fields prevent access by other modules, but do not prevent access from within the same module. The module is really the unit of encapsulation, not the struct.

The purpose of this was to eliminate the need for "friend" classes.

This sometimes conflicts with what people coming from C and C++ are used to with everything being in one file (after headers are added by the preprocessor). But having modules gives opportunities for better ways to organize the code.

As for trivial property accessors and setters, those get inlined, so are not overhead.