1 - For hardcore stuff - C++/Rust(if i can) - VM, OS, Browser, Emulator, etc..

2 - For bussiness/application/backend stuff - Swift (Go is also suitable but only if its server backend stuff, it will suck in other problem domains)

3 - for Scripting - Javascript/Lua (or Python). (This axis is expendable, as you may or may not use it)

So, from my point of view, you can also use Swift or Rust for some things, depending on the type and goal of the project, given both are memory safe and pretty fast.

You will never find 'the one true language', where you can use it for everything, so dont even loose your time trying to find it.

But for me, if theres something today that is much more closer to this goal is Swift.

Because it can cover a lot of ground. In my opinion, Rust can't do it, because given they were busy trying to eat C++ lunch in the language evolution process, they lost ergonomics and in the productivity area (you can use it of course, but you will suffer the same as if you had used C++ for the same problem domains).

Now maybe Swift will loose the Ref-counting by default runtime memory management, and if that happens, it can also be a great contender for things right now only C, C++ and Rust are suitable for.

[1] shameless plug: https://github.com/duneroadrunner/SaferCPlusPlus

edit: De-Germaning

There are use cases for C++ that Swift and Go don't fit, due to having dynamically managed memory.

Fans of D would also put D on this list. And Ada is not dead yet!