This is just a natural consequence of programming becoming more accessible, I think. And let's not pretend that C and C++ package management is "good but misunderstood"—it needs a lot of work.

Yeah, work like reading a book.

You can understand how C/C++ builds and dependencies work by reading a book, yes. But you can still criticize it—there's lots of stuff there to criticize! Modern languages have shown that dependency management and builds can be easier, faster, more secure, and more portable.

Which is why Conan and vcpkg do exist, and for quite long time OS package managers and installers.

This does not have anything to do with knowledge. C/C++ build systems are archaic if not broken.

I literally wrote a compiler but still spend 15/20% of my development time trying to find the right not user-friendly CMake syntax, understanding while my Conan dependency broke overnight, or writing header files that could be automatically generated by the compiler (à la GHC).

To me that experience sums up pretty well, apparently you were learning on how to use cmake.

As for the headers, C++20 modules, or just use an IDE like Visual Studio and the respective wizards.