I think it really depends on context. In general, it is always a great idea to learn, but we live in a society where there is a lot more to learn than time.

If a non-programmer asked me if he should learn C++, my answer would be "Only if you really, really want to. Otherwise Python, Javascript or Rust is probably a better idea".

If someone has a specific project in mind, C++ might be the answer, although probably in a minority of cases.

If someone just wants to expand their mind, then sure, why not. But there might be equally or more interesting things around, that's something that can only be retrieved from context as well.

Learning is always good, but there are subjective, qualitative nuances to be considered.