Most of my work is done in Java, .NET and JavaScript, C++ is the only native alternative that I can easily plug into all of them when I need native interop.

Go is not an option until they get their story straight with 2.0.

Swift is nice, but really it will never go beyond being an Apple platform language.

Native/Kotlin is doing its baby steps.

D seemed like a nice alternative, but they are such a small community without any big corporation support, that the language might already have lost its opportunity.

Rust would be the best alternative, but it still lacks the tooling integration story regarding IDE, graphical debuggers and OS vendors support.

Yes, no one is doing pure apps anymore in 100% C++, Java and .NET are slowly migrating to bootstrapped runtimes, but the language is not going away for the foreseeable future.

Kids are learning to program on Arduino devices using C++.

Microsoft already has some ongoing Rust projects, but Visual Rust is not yet here.

AAA Games, compilers specially LLVM and GCC, OS, HPC, Fintech, deep learning, GPGPU shaders, GUI composition engines, IoT, medical devices, car infotainment systems, VFX software might be a niche, but it is a very big niche.

One of the good things about polyglot development is that one doesn't need to silo himself/herself as developer X and be worried if language X is suitable for full stack development across all domains of computing.

EDIT: typos