>You can’t ever be a master if you worked for the whole life in the same programming language doing the same thing.

The "doing the same thing" part, you added it.

You can very much be a master if you "worked for the whole life in the same programming language" and doing multiple things with it.

But even limited to a narrow scope, you can also be a master C++ programmer doing only games programming or network services programming.

You don't have to do some of this and some of that to become a master programmer.

You might not have the domain expertise to write a database or do DSP, but a domain expertise is something different from C++ mastery.