> As a junior programmer, it made the language harder to learn.

Can you elaborate on your opinion? I mean, I don't think that argument makes any sense. You're talking about an optional feature that, under very specific circumstances, you can get the compiler to fill in for you default implementations for factory methods/constructors.

As a junior developer, it should be very clear to you that if you want to call a function, including copy constructor or copy assignment operators, you need to define them first. Is that too much of a burden to place on a junior developer?

> Although one eventually learns to avoid the anti-features (...)

There are none of those, and obviously special member functions don't pose a problem to anyone.

> Particularly when writing library code for other to use or when maintaining large codebases shared by hundreds of engineers, my experience is that complex features in the language end up used by junior engineers or require consideration in API design.

I don't think you have a good grasp on the subject. I've worked on C++ libraries shared by hundreds of engineers, and API design was always from the start the primary concern. This is not a function of seniority: it's the very basics of writing modular code intended to be consumed by third parties.

Still, special member functions are the very least of anyone's concerns because anyone remotely competent in this domain knows very well that the public interface needs to be explicitly designed to support or reject specific types of uses, and the decision of whether a component could/should be copied/moved is tied to the component's architecture and semantics.