> You have to pay attention to include order! You have to write forward declarations! You have to write include guards, in 2018!

Include order is a valid complaint, the others truly are non issues.

I mean, we have other more pressing issues. Such as the fact that garbage collection is still a thing in 2018.

> ...but nowadays a proper documentation generator gives you better...

Examples of that?

> I like seeing function-level documentation alongside interface and implementation, but if I put the documentation in both the .cpp and the .h file it's duplicated in two places and easily gets out of date.

This is the only thing that I dislike about header files. And it is a constant reminder how bad IDEs are at handling this.