Smart pointers in C often feel like trying to force a square peg into a round hole. They’re powerful, but without native language support like C++, they can lead to more complexity than they solve.
I've heard enough "C is superior to C++" arguments from game developers who then go and use header structs for inheritance, or X macros, enums, and switch statements for virtual functions, to know that more complexity isn't an issue as long as people feel clever and validated.
I love using x macros with c++ to create static types and hooks to disambiguate from basic types. This is more applicable to final executables than libraries - I would never provide anyone with an API based on the mess it creates, but it allows application code to be strongly checked and makes it really easy to add whole classes of assertions to debug builds.
I never said X macros are bad on their own. With C++ you can code exactly as you would in C, but you don't have to manually implement C++ features when there's a need. C++ doesn't have any more problems than C, it's programmers who abuse language features that creates problems.
I don't think they do those things for validation. They do those things for control. Even c++ game developers create there own entire standard library replacements.