I'm not sure I'm ready to learn another language to be honest. After a decade+ of C++ it'd feel like driving on the wrong side of the road and I wouldn't blame any employers who didn't want to take a chance on that :)
Usually it's not the programming language that's important, but the ecosystem around the language (the standard library, available libraries, interests of the community etc...). Programming languages are mostly interchangeable, but their ecosystems are not. Some are more suited for server backend work, some for writing UI applications, some for scripting and automation, etc...
After a while (and a few languages under your belt) you'll select a language based on a project's requirement, instead of trying to shoehorn every project into your favourite programming language. IME the multi-language approach is much more fun and fullfilling.
I no longer consider an ecosystem separate from a programming language given its importance in the overall utility of the language.
I came to that conclusion after I realized I wouldn’t like the Rust language so much if it weren’t for cargo and the crates.io package manager.
I know a guy who hold the opinion that Docker is a sufficient package manager for C++. I think this misses the degree to which tight coupling of these technologies can yield a lot of leverage.
Well, you/they practised at least C++98, C++11, C++17... That's many different languages already ;-)